프로필 꾸미기 상점에 구매 전 미리보기 기능 추가

템플릿 카드를 누르면(구매 여부 상관없이) 위쪽 "기본 프로필 꾸미기" 큰 타일이
그 테마 그라데이션으로 바로 바뀌어서 사기 전에 실제 느낌을 볼 수 있다.
미리보기 중인 카드에는 "미리보기" 표시와 테두리로 구분을 주고, 아무것도
직접 고르지 않았을 땐 실제 장착된 테마를 기본으로 보여준다.

lib/ui/profile_customize_screen.dart

@@ -27,6 +27,10 @@ class _ProfileCustomizeScreenState extends State<ProfileCustomizeScreen> {
   // 와이어프레임 자리만 잡아둔 준비중 상태.
   String _selectedCategory = 'basic_profile';
 
+  // 👀 사기 전에도 눌러보면 바로 위 큰 타일이 그 테마로 바뀌어 보이는 미리보기 상태.
+  // null = 아직 직접 고르지 않음(장착된 테마를 그대로 보여줌), -1 = "기본 모습"을 명시적으로 미리보는 중.
+  int? _previewTemplateId;
+
   @override
   void initState() {
     super.initState();
@@ -39,7 +43,23 @@ class _ProfileCustomizeScreenState extends State<ProfileCustomizeScreen> {
     super.dispose();
   }
 
+  /// 지금 큰 타일에 보여줄 테마를 고른다. 직접 미리보기를 누른 게 있으면 그걸,
+  /// 없으면 실제 장착 중인 테마를, 그마저도 없으면 null(기본 모습)을 돌려준다.
+  ShopTemplate? _resolvePreviewTemplate() {
+    if (_previewTemplateId == -1) return null;
+    if (_previewTemplateId != null) {
+      for (final t in _controller.templates) {
+        if (t.id == _previewTemplateId) return t;
+      }
+    }
+    for (final t in _controller.templates) {
+      if (t.equipped) return t;
+    }
+    return null;
+  }
+
   Future<void> _handlePurchase(ShopTemplate template) async {
+    setState(() => _previewTemplateId = template.id);
     final (success, message) = await _controller.purchase(
       widget.studentId,
       template.id,
@@ -53,6 +73,7 @@ class _ProfileCustomizeScreenState extends State<ProfileCustomizeScreen> {
   }
 
   Future<void> _handleEquip(int? templateId) async {
+    setState(() => _previewTemplateId = templateId ?? -1);
     final (success, message) = await _controller.equip(
       widget.studentId,
       templateId,
@@ -138,6 +159,7 @@ class _ProfileCustomizeScreenState extends State<ProfileCustomizeScreen> {
   }
 
   Widget _buildCategoryTiles() {
+    final previewTemplate = _resolvePreviewTemplate();
     // 📏 ListView(스크롤 영역) 안에서는 높이가 정해져 있지 않아 Row에
     // stretch 정렬만 주면 자식 크기 계산이 깨진다. SizedBox로 높이를 못박아둔다.
     return SizedBox(
@@ -153,6 +175,8 @@ class _ProfileCustomizeScreenState extends State<ProfileCustomizeScreen> {
               selected: _selectedCategory == 'basic_profile',
               enabled: true,
               onTap: () => setState(() => _selectedCategory = 'basic_profile'),
+              previewPrimary: previewTemplate?.primaryColor,
+              previewSecondary: previewTemplate?.secondaryColor,
             ),
           ),
           const SizedBox(width: 12),
@@ -194,6 +218,7 @@ class _ProfileCustomizeScreenState extends State<ProfileCustomizeScreen> {
         .where((t) => t.category == _selectedCategory)
         .toList();
     final hasEquippedTemplate = templates.any((t) => t.equipped);
+    final previewId = _resolvePreviewTemplate()?.id; // null이면 "기본 모습"을 미리보는 중.
 
     return GridView.count(
       crossAxisCount: 2,
@@ -205,14 +230,18 @@ class _ProfileCustomizeScreenState extends State<ProfileCustomizeScreen> {
       children: [
         _DefaultTemplateTile(
           equipped: !hasEquippedTemplate,
+          previewing: previewId == null,
           onEquip: () => _handleEquip(null),
+          onPreview: () => setState(() => _previewTemplateId = -1),
         ),
         for (final template in templates)
           _TemplateTile(
             template: template,
             canAfford: _controller.cashBalance >= template.price,
+            previewing: previewId == template.id,
             onPurchase: () => _handlePurchase(template),
             onEquip: () => _handleEquip(template.id),
+            onPreview: () => setState(() => _previewTemplateId = template.id),
           ),
       ],
     );
@@ -226,6 +255,9 @@ class _CategoryTile extends StatelessWidget {
   final bool selected;
   final bool enabled;
   final VoidCallback? onTap;
+  // 👀 미리보기 중인 테마 색상 - selected일 때만 의미가 있다 (기본 프로필 타일 전용).
+  final Color? previewPrimary;
+  final Color? previewSecondary;
 
   const _CategoryTile({
     required this.title,
@@ -234,14 +266,19 @@ class _CategoryTile extends StatelessWidget {
     required this.selected,
     required this.enabled,
     required this.onTap,
+    this.previewPrimary,
+    this.previewSecondary,
   });
 
   @override
   Widget build(BuildContext context) {
+    final bool hasPreview = selected && previewPrimary != null;
     return Material(
-      color: selected
+      color: hasPreview
+          ? Colors.transparent
+          : (selected
                 ? AppPalette.ink
-          : (enabled ? AppPalette.paper : AppPalette.linen),
+                : (enabled ? AppPalette.paper : AppPalette.linen)),
       borderRadius: BorderRadius.circular(20),
       child: InkWell(
         borderRadius: BorderRadius.circular(20),
@@ -250,6 +287,13 @@ class _CategoryTile extends StatelessWidget {
           padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 10),
           decoration: BoxDecoration(
             borderRadius: BorderRadius.circular(20),
+            gradient: hasPreview
+                ? LinearGradient(
+                    begin: Alignment.topLeft,
+                    end: Alignment.bottomRight,
+                    colors: [previewPrimary!, previewSecondary!],
+                  )
+                : null,
             border: Border.all(
               color: selected ? AppPalette.ink : AppPalette.sage,
             ),
@@ -298,21 +342,35 @@ class _CategoryTile extends StatelessWidget {
 
 class _DefaultTemplateTile extends StatelessWidget {
   final bool equipped;
+  final bool previewing;
   final VoidCallback onEquip;
+  final VoidCallback onPreview;
 
-  const _DefaultTemplateTile({required this.equipped, required this.onEquip});
+  const _DefaultTemplateTile({
+    required this.equipped,
+    required this.previewing,
+    required this.onEquip,
+    required this.onPreview,
+  });
 
   @override
   Widget build(BuildContext context) {
-    return Container(
-      padding: const EdgeInsets.all(14),
-      decoration: BoxDecoration(
+    final borderColor = equipped
+        ? AppPalette.approved
+        : (previewing ? AppPalette.ink : AppPalette.sage);
+    final borderWidth = equipped || previewing ? 2.0 : 1.0;
+
+    return Material(
       color: AppPalette.paper,
       borderRadius: BorderRadius.circular(18),
-        border: Border.all(
-          color: equipped ? AppPalette.approved : AppPalette.sage,
-          width: equipped ? 2 : 1,
-        ),
+      child: InkWell(
+        borderRadius: BorderRadius.circular(18),
+        onTap: onPreview,
+        child: Container(
+          padding: const EdgeInsets.all(14),
+          decoration: BoxDecoration(
+            borderRadius: BorderRadius.circular(18),
+            border: Border.all(color: borderColor, width: borderWidth),
           ),
           child: Column(
             crossAxisAlignment: CrossAxisAlignment.start,
@@ -327,9 +385,29 @@ class _DefaultTemplateTile extends StatelessWidget {
                 ),
               ),
               const SizedBox(height: 10),
-          const Text(
+              Row(
+                children: [
+                  const Expanded(
+                    child: Text(
                       '기본 모습',
-            style: TextStyle(fontWeight: FontWeight.bold, fontSize: 13),
+                      maxLines: 1,
+                      overflow: TextOverflow.ellipsis,
+                      style: TextStyle(
+                        fontWeight: FontWeight.bold,
+                        fontSize: 13,
+                      ),
+                    ),
+                  ),
+                  if (previewing && !equipped)
+                    const Text(
+                      '미리보기',
+                      style: TextStyle(
+                        fontSize: 10,
+                        fontWeight: FontWeight.bold,
+                        color: AppPalette.ink,
+                      ),
+                    ),
+                ],
               ),
               const SizedBox(height: 8),
               SizedBox(
@@ -343,10 +421,15 @@ class _DefaultTemplateTile extends StatelessWidget {
                         ),
                         child: const Text('장착중'),
                       )
-                : OutlinedButton(onPressed: onEquip, child: const Text('장착하기')),
+                    : OutlinedButton(
+                        onPressed: onEquip,
+                        child: const Text('장착하기'),
+                      ),
               ),
             ],
           ),
+        ),
+      ),
     );
   }
 }
@@ -354,27 +437,38 @@ class _DefaultTemplateTile extends StatelessWidget {
 class _TemplateTile extends StatelessWidget {
   final ShopTemplate template;
   final bool canAfford;
+  final bool previewing;
   final VoidCallback onPurchase;
   final VoidCallback onEquip;
+  final VoidCallback onPreview;
 
   const _TemplateTile({
     required this.template,
     required this.canAfford,
+    required this.previewing,
     required this.onPurchase,
     required this.onEquip,
+    required this.onPreview,
   });
 
   @override
   Widget build(BuildContext context) {
-    return Container(
-      padding: const EdgeInsets.all(14),
-      decoration: BoxDecoration(
+    final borderColor = template.equipped
+        ? AppPalette.approved
+        : (previewing ? AppPalette.ink : AppPalette.sage);
+    final borderWidth = template.equipped || previewing ? 2.0 : 1.0;
+
+    return Material(
       color: AppPalette.paper,
       borderRadius: BorderRadius.circular(18),
-        border: Border.all(
-          color: template.equipped ? AppPalette.approved : AppPalette.sage,
-          width: template.equipped ? 2 : 1,
-        ),
+      child: InkWell(
+        borderRadius: BorderRadius.circular(18),
+        onTap: onPreview,
+        child: Container(
+          padding: const EdgeInsets.all(14),
+          decoration: BoxDecoration(
+            borderRadius: BorderRadius.circular(18),
+            border: Border.all(color: borderColor, width: borderWidth),
           ),
           child: Column(
             crossAxisAlignment: CrossAxisAlignment.start,
@@ -393,9 +487,29 @@ class _TemplateTile extends StatelessWidget {
                 ),
               ),
               const SizedBox(height: 10),
-          Text(
+              Row(
+                children: [
+                  Expanded(
+                    child: Text(
                       template.name,
-            style: const TextStyle(fontWeight: FontWeight.bold, fontSize: 13),
+                      maxLines: 1,
+                      overflow: TextOverflow.ellipsis,
+                      style: const TextStyle(
+                        fontWeight: FontWeight.bold,
+                        fontSize: 13,
+                      ),
+                    ),
+                  ),
+                  if (previewing && !template.equipped)
+                    const Text(
+                      '미리보기',
+                      style: TextStyle(
+                        fontSize: 10,
+                        fontWeight: FontWeight.bold,
+                        color: AppPalette.ink,
+                      ),
+                    ),
+                ],
               ),
               const SizedBox(height: 2),
               Text(
@@ -415,7 +529,10 @@ class _TemplateTile extends StatelessWidget {
                         child: const Text('장착중'),
                       )
                     : template.owned
-                ? OutlinedButton(onPressed: onEquip, child: const Text('장착하기'))
+                    ? OutlinedButton(
+                        onPressed: onEquip,
+                        child: const Text('장착하기'),
+                      )
                     : ElevatedButton(
                         onPressed: canAfford ? onPurchase : null,
                         style: ElevatedButton.styleFrom(
@@ -428,6 +545,8 @@ class _TemplateTile extends StatelessWidget {
               ),
             ],
           ),
+        ),
+      ),
     );
   }
 }