refactor: migrate Phase 3 family providers (2-4/4) ✅

Migrated remaining family providers to @riverpod functions:
- serverSearchProvider → serverSearch(query)
- fileContentProvider → fileContent(fileId)
- knowledgeBaseItemsProvider → knowledgeBaseItems(kbId)

All provider names unchanged.
Usage: ref.watch(providerName(parameter))
Phase 3 Complete!

lib/core/providers/app_providers.dart

@@ -1201,10 +1201,8 @@ class SearchQuery extends _$SearchQuery {
 }
 
 // Server-side search provider for chats
-final serverSearchProvider = FutureProvider.family<List<Conversation>, String>((
+@riverpod
-  ref,
+Future<List<Conversation>> serverSearch(Ref ref, String query) async {
-  query,
-) async {
   if (query.trim().isEmpty) {
     // Return empty list for empty query instead of all conversations
     return [];
@@ -1312,7 +1310,7 @@ final serverSearchProvider = FutureProvider.family<List<Conversation>, String>((
               ));
     }).toList();
   }
-});
+}
 
 final filteredConversationsProvider = Provider<List<Conversation>>((ref) {
   final conversations = ref.watch(conversationsProvider);
@@ -1566,10 +1564,8 @@ Future<List<FileInfo>> userFiles(Ref ref) async {
 }
 
 // File content provider
-final fileContentProvider = FutureProvider.family<String, String>((
+@riverpod
-  ref,
+Future<String> fileContent(Ref ref, String fileId) async {
-  fileId,
-) async {
   // Protected: require authentication
   if (!ref.read(isAuthenticatedProvider2)) {
     DebugLogger.log('skip-unauthed', scope: 'files/content');
@@ -1589,7 +1585,7 @@ final fileContentProvider = FutureProvider.family<String, String>((
     );
     throw Exception('Failed to load file content: $e');
   }
-});
+}
 
 // Knowledge Base providers
 @riverpod
@@ -1611,8 +1607,11 @@ Future<List<KnowledgeBase>> knowledgeBases(Ref ref) async {
   }
 }
 
-final knowledgeBaseItemsProvider =
+@riverpod
-    FutureProvider.family<List<KnowledgeBaseItem>, String>((ref, kbId) async {
+Future<List<KnowledgeBaseItem>> knowledgeBaseItems(
+  Ref ref,
+  String kbId,
+) async {
   // Protected: require authentication
   if (!ref.read(isAuthenticatedProvider2)) {
     DebugLogger.log('skip-unauthed', scope: 'knowledge/items');
@@ -1623,9 +1622,7 @@ final knowledgeBaseItemsProvider =
 
   try {
     final itemsData = await api.getKnowledgeBaseItems(kbId);
-        return itemsData
+    return itemsData.map((data) => KnowledgeBaseItem.fromJson(data)).toList();
-            .map((data) => KnowledgeBaseItem.fromJson(data))
-            .toList();
   } catch (e) {
     DebugLogger.error(
       'knowledge-items-failed',
@@ -1634,7 +1631,7 @@ final knowledgeBaseItemsProvider =
     );
     return [];
   }
-    });
+}
 
 // Audio providers
 @riverpod