feat: Add feed filtering UI with FeedFilterButton and integrate into personal feed

sojorn_app/lib/screens/home/feed_personal_screen.dart

@@ -7,6 +7,7 @@ import '../../models/feed_filter.dart';
 import '../../theme/app_theme.dart';
 import '../../widgets/sojorn_post_card.dart';
 import '../../widgets/app_scaffold.dart';
+import '../../widgets/feed_filter_button.dart';
 import '../compose/compose_screen.dart';
 import '../post/post_detail_screen.dart';
 import '../../widgets/first_use_hint.dart';
@@ -54,6 +55,7 @@ class _FeedPersonalScreenState extends ConsumerState<FeedPersonalScreen> {
       final posts = await apiService.getPersonalFeed(
         limit: 50,
         offset: refresh ? 0 : _posts.length,
+        filterType: _currentFilter.typeValue,
       );
 
       _setStateIfMounted(() {
@@ -93,6 +95,11 @@ class _FeedPersonalScreenState extends ConsumerState<FeedPersonalScreen> {
     FocusManager.instance.primaryFocus?.unfocus();
   }
 
+  void _onFilterChanged(FeedFilter filter) {
+    setState(() => _currentFilter = filter);
+    _loadPosts(refresh: true);
+  }
+
   @override
   Widget build(BuildContext context) {
     ref.listen<int>(feedRefreshProvider, (_, __) {
@@ -102,6 +109,12 @@ class _FeedPersonalScreenState extends ConsumerState<FeedPersonalScreen> {
     return AppScaffold(
       title: '',
       showAppBar: false,
+      actions: [
+        FeedFilterButton(
+          currentFilter: _currentFilter,
+          onFilterChanged: _onFilterChanged,
+        ),
+      ],
       body: _error != null
           ? _ErrorState(
               message: _error!,

sojorn_app/lib/screens/profile/viewable_profile_screen.dart

@@ -25,6 +25,7 @@ import '../post/post_detail_screen.dart';
 import 'profile_settings_screen.dart';
 import 'followers_following_screen.dart';
 import '../../widgets/harmony_explainer_modal.dart';
+import '../../widgets/follow_button.dart';
 
 /// Unified profile screen - handles both own profile and viewing others.
 ///
@@ -70,6 +71,8 @@ class _UnifiedProfileScreenState extends ConsumerState<UnifiedProfileScreen>
   bool _isCreatingProfile = false;
   ProfilePrivacySettings? _privacySettings;
   bool _isPrivacyLoading = false;
+  List<Map<String, dynamic>> _mutualFollowers = [];
+  bool _isMutualFollowersLoading = false;
 
   /// True when no handle was provided (bottom-nav profile tab)
   bool get _isOwnProfileMode => widget.handle == null;

sojorn_app/lib/services/api_service.dart

@@ -1360,14 +1360,30 @@ class ApiService {
   // Notifications & Feed (Missing Methods)
   // =========================================================================
 
-  Future<List<Post>> getPersonalFeed({int limit = 20, int offset = 0}) async {
-    final data = await callGoApi(
-      '/feed',
+  Future<List<Post>> getPersonalFeed({
+    int limit = 20,
+    int offset = 0,
+    String? filterType,
+  }) async {
+    final queryParams = {
+      'limit': '$limit',
+      'offset': '$offset',
+    };
+    if (filterType != null) {
+      queryParams['type'] = filterType;
+    }
+    
+    final data = await _callGoApi(
+      '/feed/personal',
       method: 'GET',
-      queryParams: {'limit': '$limit', 'offset': '$offset'},
+      queryParams: queryParams,
     );
-    final posts = data['posts'] as List? ?? [];
-    return posts.map((p) => Post.fromJson(p)).toList();
+    if (data['posts'] != null) {
+      return (data['posts'] as List)
+          .map((json) => Post.fromJson(json))
+          .toList();
+    }
+    return [];
   }
 
   Future<List<Post>> getSojornFeed({int limit = 20, int offset = 0}) async {

sojorn_app/lib/widgets/feed_filter_button.dart

@@ -0,0 +1,52 @@
+import 'package:flutter/material.dart';
+import '../models/feed_filter.dart';
+import '../theme/app_theme.dart';
+
+/// Filter button for feed screens with popup menu
+class FeedFilterButton extends StatelessWidget {
+  final FeedFilter currentFilter;
+  final ValueChanged<FeedFilter> onFilterChanged;
+
+  const FeedFilterButton({
+    super.key,
+    required this.currentFilter,
+    required this.onFilterChanged,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return PopupMenuButton<FeedFilter>(
+      icon: Icon(
+        Icons.filter_list,
+        color: currentFilter != FeedFilter.all ? AppTheme.navyBlue : null,
+      ),
+      initialValue: currentFilter,
+      onSelected: onFilterChanged,
+      tooltip: 'Filter posts',
+      itemBuilder: (context) => [
+        _buildMenuItem(FeedFilter.all, Icons.apps),
+        _buildMenuItem(FeedFilter.posts, Icons.article_outlined),
+        _buildMenuItem(FeedFilter.quips, Icons.play_circle_outline),
+        _buildMenuItem(FeedFilter.chains, Icons.forum_outlined),
+        _buildMenuItem(FeedFilter.beacons, Icons.sensors),
+      ],
+    );
+  }
+
+  PopupMenuItem<FeedFilter> _buildMenuItem(FeedFilter filter, IconData icon) {
+    return PopupMenuItem(
+      value: filter,
+      child: Row(
+        children: [
+          Icon(icon, size: 20),
+          const SizedBox(width: 12),
+          Text(filter.label),
+          if (filter == currentFilter) ...[
+            const Spacer(),
+            Icon(Icons.check, size: 18, color: AppTheme.navyBlue),
+          ],
+        ],
+      ),
+    );
+  }
+}