Group the Sources tab by kind and pick a kind when adding a feed (#4)

The Sources tab shows News, Learning and Fun sections, each split by
language; kinds or languages without Sources get no header. The add-feed
dialog has a kind picker that defaults to News.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/ui/sources_screen.dart

@@ -40,29 +40,7 @@ class SourcesScreen extends StatelessWidget {
           body: ListView(
             padding: const EdgeInsets.only(bottom: 96),
             children: [
-              for (final lang in SourceLanguage.values) ...[
-                Padding(
-                  padding: const EdgeInsets.fromLTRB(16, 16, 16, 4),
-                  child: Text('${lang.flag}  ${lang.label}',
-                      style: theme.textTheme.titleSmall
-                          ?.copyWith(color: theme.colorScheme.primary)),
-                ),
-                for (final source in state.allSources.where((s) => s.language == lang))
-                  _SourceTile(
-                    source: source,
-                    enabled: state.enabledSourceIds.contains(source.id),
-                    onToggle: (v) {
-                      state.setSourceEnabled(source, v);
-                      onChanged();
-                    },
-                    onDelete: source.isCustom
-                        ? () {
-                            state.removeCustomSource(source);
-                            onChanged();
-                          }
-                        : null,
-                  ),
-              ],
+              for (final kind in SourceKind.values) ..._kindSection(context, kind),
             ],
           ),
         );
@@ -70,6 +48,44 @@ class SourcesScreen extends StatelessWidget {
     );
   }
 
+  /// One section per kind, split by language. Kinds and languages without
+  /// Sources are left out instead of showing an empty header.
+  List<Widget> _kindSection(BuildContext context, SourceKind kind) {
+    final theme = Theme.of(context);
+    final sources = state.allSources.where((s) => s.kind == kind).toList();
+    if (sources.isEmpty) return const [];
+    return [
+      Padding(
+        padding: const EdgeInsets.fromLTRB(16, 24, 16, 0),
+        child: Text(kind.label, style: theme.textTheme.titleMedium),
+      ),
+      for (final lang in SourceLanguage.values)
+        if (sources.any((s) => s.language == lang)) ...[
+          Padding(
+            padding: const EdgeInsets.fromLTRB(16, 12, 16, 4),
+            child: Text('${lang.flag}  ${lang.label}',
+                style: theme.textTheme.titleSmall
+                    ?.copyWith(color: theme.colorScheme.primary)),
+          ),
+          for (final source in sources.where((s) => s.language == lang))
+            _SourceTile(
+              source: source,
+              enabled: state.enabledSourceIds.contains(source.id),
+              onToggle: (v) {
+                state.setSourceEnabled(source, v);
+                onChanged();
+              },
+              onDelete: source.isCustom
+                  ? () {
+                      state.removeCustomSource(source);
+                      onChanged();
+                    }
+                  : null,
+            ),
+        ],
+    ];
+  }
+
   Future<void> _addFeed(BuildContext context) async {
     final added = await showDialog<bool>(
       context: context,
@@ -134,6 +150,7 @@ class _AddFeedDialogState extends State<_AddFeedDialog> {
   final _name = TextEditingController();
   final _url = TextEditingController();
   SourceLanguage _language = SourceLanguage.de;
+  SourceKind _kind = SourceKind.news;
   bool _busy = false;
   String? _error;
 
@@ -156,7 +173,7 @@ class _AddFeedDialogState extends State<_AddFeedDialog> {
       _error = null;
     });
     final error = await widget.state
-        .addCustomSource(name: name, feedUrl: url, language: _language);
+        .addCustomSource(name: name, feedUrl: url, language: _language, kind: _kind);
     if (!mounted) return;
     if (error == null) {
       Navigator.pop(context, true);
@@ -199,6 +216,15 @@ class _AddFeedDialogState extends State<_AddFeedDialog> {
               selected: {_language},
               onSelectionChanged: (s) => setState(() => _language = s.first),
             ),
+            const SizedBox(height: 12),
+            SegmentedButton<SourceKind>(
+              segments: [
+                for (final k in SourceKind.values)
+                  ButtonSegment(value: k, label: Text(k.label)),
+              ],
+              selected: {_kind},
+              onSelectionChanged: (s) => setState(() => _kind = s.first),
+            ),
             if (_error != null) ...[
               const SizedBox(height: 12),
               Text(_error!, style: TextStyle(color: Theme.of(context).colorScheme.error)),