feat: implement initial Electron chat application with core UI components and Convex backend integration.

Frontend/Electron/src/components/Sidebar.jsx

@@ -152,10 +152,20 @@ const UserControlPanel = ({ username, userId }) => {
         if (window.sessionPersistence) {
             try { await window.sessionPersistence.clear(); } catch {}
         }
-        // Clear storage (preserve theme)
+        // Clear storage (preserve theme and user preferences)
         const theme = localStorage.getItem('theme');
+        const savedPrefs = {};
+        for (let i = 0; i < localStorage.length; i++) {
+            const key = localStorage.key(i);
+            if (key.startsWith('userPrefs_')) {
+                savedPrefs[key] = localStorage.getItem(key);
+            }
+        }
         localStorage.clear();
         if (theme) localStorage.setItem('theme', theme);
+        for (const [key, value] of Object.entries(savedPrefs)) {
+            localStorage.setItem(key, value);
+        }
         sessionStorage.clear();
         navigate('/');
     };
@@ -749,7 +759,15 @@ const Sidebar = ({ channels, categories, activeChannel, onSelectChannel, usernam
     const [newChannelType, setNewChannelType] = useState('text');
     const [editingChannel, setEditingChannel] = useState(null);
     const [isScreenShareModalOpen, setIsScreenShareModalOpen] = useState(false);
-    const [collapsedCategories, setCollapsedCategories] = useState(() => getUserPref(userId, 'collapsedCategories', {}));
+    const [collapsedCategories, setCollapsedCategories] = useState(() => {
+        const effectiveUserId = userId || localStorage.getItem('userId');
+        return getUserPref(effectiveUserId, 'collapsedCategories', {});
+    });
+    useEffect(() => {
+        if (userId) {
+            setCollapsedCategories(getUserPref(userId, 'collapsedCategories', {}));
+        }
+    }, [userId]);
     const [channelListContextMenu, setChannelListContextMenu] = useState(null);
     const [voiceUserMenu, setVoiceUserMenu] = useState(null);
     const [showCreateChannelModal, setShowCreateChannelModal] = useState(false);
@@ -1107,11 +1125,9 @@ const Sidebar = ({ channels, categories, activeChannel, onSelectChannel, usernam
     };
 
     const toggleCategory = (cat) => {
-        setCollapsedCategories(prev => {
-            const next = { ...prev, [cat]: !prev[cat] };
-            setUserPref(userId, 'collapsedCategories', next);
-            return next;
-        });
+        const next = { ...collapsedCategories, [cat]: !collapsedCategories[cat] };
+        setCollapsedCategories(next);
+        setUserPref(userId, 'collapsedCategories', next);
     };
 
     // Group channels by categoryId