feat(projects): add Projects tab with load/delete list

lib/main.dart

@@ -84,7 +84,7 @@ enum CatalogViewMode { list, grid }
 
 enum ColorExtractionMode { dominant, average }
 
-enum HomeSection { mosaic, catalog }
+enum HomeSection { mosaic, catalog, projects }
 
 class MosaicHomePage extends StatefulWidget {
   const MosaicHomePage({super.key});
@@ -116,6 +116,7 @@ class _MosaicHomePageState extends State<MosaicHomePage>
   bool _isCaptureFlowInProgress = false;
   bool _isRecoveringCapture = false;
   bool _isProjectBusy = false;
+  List<File> _projectFiles = [];
 
   double _fidelityStructure = 0.5;
   double _ditheringStrength = 0.35;
@@ -133,6 +134,7 @@ class _MosaicHomePageState extends State<MosaicHomePage>
     _gridHeightCtrl.addListener(_scheduleRegenerate);
     _capSizeCtrl.addListener(_scheduleRegenerate);
     _loadCatalog();
+    _refreshProjectFiles();
     WidgetsBinding.instance.addPostFrameCallback((_) {
       _recoverCaptureOnResumeOrStart();
       _loadProject(silent: true);
@@ -177,16 +179,42 @@ class _MosaicHomePageState extends State<MosaicHomePage>
     return file.path;
   }
 
-  Future<File> _projectFile() async {
+  Future<Directory> _projectsDir() async {
     final docs = await getApplicationDocumentsDirectory();
-    return File('${docs.path}/mosaic_project.json');
+    final dir = Directory('${docs.path}/projects');
+    await dir.create(recursive: true);
+    return dir;
+  }
+
+  String _projectFilename() {
+    final now = DateTime.now();
+    final stamp = now
+        .toIso8601String()
+        .replaceAll(':', '-')
+        .replaceAll('.', '-')
+        .replaceAll('T', '_');
+    return 'project_$stamp.json';
+  }
+
+  Future<void> _refreshProjectFiles() async {
+    try {
+      final dir = await _projectsDir();
+      final files = dir
+          .listSync()
+          .whereType<File>()
+          .where((f) => f.path.endsWith('.json'))
+          .toList()
+        ..sort((a, b) => b.path.compareTo(a.path));
+      if (mounted) setState(() => _projectFiles = files);
+    } catch (_) {}
   }
 
   Future<void> _saveProject({bool silent = false}) async {
     if (_isProjectBusy) return;
     _isProjectBusy = true;
     try {
-      final file = await _projectFile();
+      final projectsDir = await _projectsDir();
+      final file = File('${projectsDir.path}/${_projectFilename()}');
       final payload = <String, dynamic>{
         'useCapSize': _useCapSize,
         'gridWidth': _gridWidthCtrl.text,
@@ -197,11 +225,11 @@ class _MosaicHomePageState extends State<MosaicHomePage>
         'edgeEmphasis': _edgeEmphasis,
         'colorVariation': _colorVariation,
         'selectedPreset': _selectedPreset.name,
-        'activeSection': _activeSection.name,
         'sourceImageBase64':
             _sourceImageBytes == null ? null : base64Encode(_sourceImageBytes!),
       };
       await file.writeAsString(jsonEncode(payload), flush: true);
+      await _refreshProjectFiles();
       if (!silent && mounted) {
         ScaffoldMessenger.of(context).showSnackBar(
           const SnackBar(content: Text('Projekt gespeichert ✅')),
@@ -218,15 +246,19 @@ class _MosaicHomePageState extends State<MosaicHomePage>
     }
   }
 
-  Future<void> _loadProject({bool silent = false}) async {
+  Future<void> _loadProject({bool silent = false, File? fromFile}) async {
     if (_isProjectBusy) return;
     _isProjectBusy = true;
     try {
-      final file = await _projectFile();
+      File? file = fromFile;
+      if (file == null) {
+        await _refreshProjectFiles();
+        if (_projectFiles.isEmpty) return;
+        file = _projectFiles.first;
+      }
       if (!await file.exists()) return;
-      final data =
-          jsonDecode(await file.readAsString()) as Map<String, dynamic>;
 
+      final data = jsonDecode(await file.readAsString()) as Map<String, dynamic>;
       final sourceB64 = data['sourceImageBase64'] as String?;
       final source = sourceB64 == null ? null : base64Decode(sourceB64);
 
@@ -253,21 +285,14 @@ class _MosaicHomePageState extends State<MosaicHomePage>
           orElse: () => _selectedPreset,
         );
 
-        final sectionName = data['activeSection'] as String?;
-        _activeSection = HomeSection.values.firstWhere(
-          (s) => s.name == sectionName,
-          orElse: () => _activeSection,
-        );
-
         if (source != null) {
           _sourceImageBytes = source;
           _result = null;
         }
+        _activeSection = HomeSection.mosaic;
       });
 
-      if (source != null) {
+      if (source != null) await _generate();
-        await _generate();
-      }
       if (!silent && mounted) {
         ScaffoldMessenger.of(context).showSnackBar(
           const SnackBar(content: Text('Projekt geladen ✅')),
@@ -284,6 +309,24 @@ class _MosaicHomePageState extends State<MosaicHomePage>
     }
   }
 
+  Future<void> _deleteProject(File file) async {
+    try {
+      await file.delete();
+      await _refreshProjectFiles();
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('Projekt gelöscht')),
+        );
+      }
+    } catch (_) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('Löschen fehlgeschlagen')),
+        );
+      }
+    }
+  }
+
   Future<void> _loadCatalog() async {
     final defaults = [
       CapCatalogEntry.newEntry(name: 'White', color: const Color(0xFFF2F2F2)),
@@ -824,7 +867,9 @@ class _MosaicHomePageState extends State<MosaicHomePage>
         backgroundColor: Colors.white.withValues(alpha: 0.45),
         title: Text(_activeSection == HomeSection.mosaic
             ? 'Bottle-Cap Mosaic Studio'
-            : 'Cap Catalog'),
+            : _activeSection == HomeSection.catalog
+                ? 'Cap Catalog'
+                : 'Projekte'),
       ),
       floatingActionButton: _activeSection == HomeSection.mosaic
           ? FloatingActionButton.extended(
@@ -847,7 +892,9 @@ class _MosaicHomePageState extends State<MosaicHomePage>
               ? const Center(child: CircularProgressIndicator())
               : _activeSection == HomeSection.mosaic
                   ? _buildMosaicScreen()
-                  : _buildCatalogScreen(),
+                  : _activeSection == HomeSection.catalog
+                      ? _buildCatalogScreen()
+                      : _buildProjectsScreen(),
         ],
       ),
       bottomNavigationBar: NavigationBar(
@@ -866,11 +913,54 @@ class _MosaicHomePageState extends State<MosaicHomePage>
             selectedIcon: Icon(Icons.inventory_2),
             label: 'Catalog',
           ),
+          NavigationDestination(
+            icon: Icon(Icons.folder_copy_outlined),
+            selectedIcon: Icon(Icons.folder_copy),
+            label: 'Projekte',
+          ),
         ],
       ),
     );
   }
 
+  Widget _buildProjectsScreen() {
+    if (_projectFiles.isEmpty) {
+      return const Center(child: Text('Noch keine gespeicherten Projekte.'));
+    }
+
+    return ListView.builder(
+      padding: const EdgeInsets.all(14),
+      itemCount: _projectFiles.length,
+      itemBuilder: (context, index) {
+        final file = _projectFiles[index];
+        final name = file.uri.pathSegments.isEmpty
+            ? file.path
+            : file.uri.pathSegments.last;
+        return Card(
+          child: ListTile(
+            leading: const Icon(Icons.insert_drive_file_outlined),
+            title: Text(name),
+            trailing: Wrap(
+              spacing: 8,
+              children: [
+                IconButton(
+                  tooltip: 'Laden',
+                  icon: const Icon(Icons.playlist_add_check_circle_outlined),
+                  onPressed: () => _loadProject(fromFile: file),
+                ),
+                IconButton(
+                  tooltip: 'Löschen',
+                  icon: const Icon(Icons.delete_outline),
+                  onPressed: () => _deleteProject(file),
+                ),
+              ],
+            ),
+          ),
+        );
+      },
+    );
+  }
+
   Widget _buildMosaicScreen() {
     return Padding(
       padding: const EdgeInsets.all(14),