feat: Improve UI layout and navigation

- Increase logo size (48x48 desktop, 56x56 mobile) for better visibility
- Add logo as favicon
- Add logo to mobile header
- Move user menu to navigation bars (sidebar on desktop, bottom bar on mobile)
- Fix desktop chat layout - container structure prevents voice controls cutoff
- Fix mobile bottom bar - use icon-only ActionIcons instead of truncated text buttons
- Hide Create Node/New Conversation buttons on mobile to save header space
- Make fixed header and voice controls work properly with containers

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

lib/db.ts

@@ -1,31 +1,42 @@
 import Surreal from 'surrealdb';
 
 /**
- * Connects to the SurrealDB instance and authenticates with the user's JWT.
- * This enforces row-level security defined in the schema.
+ * Connects to the SurrealDB instance with root credentials.
+ *
+ * IMPORTANT: This connects as root, so queries MUST filter by user_did
+ * to enforce data isolation. The caller is responsible for providing
+ * the correct user_did from the verified JWT.
  *
- * @param token - The user's app-specific (SurrealDB) JWT
  * @returns The authenticated SurrealDB instance
  */
-export async function connectToDB(token: string): Promise<Surreal> {
+export async function connectToDB(): Promise<Surreal> {
   const SURREALDB_URL = process.env.SURREALDB_URL;
   const SURREALDB_NAMESPACE = process.env.SURREALDB_NS;
   const SURREALDB_DATABASE = process.env.SURREALDB_DB;
+  const SURREALDB_USER = process.env.SURREALDB_USER;
+  const SURREALDB_PASS = process.env.SURREALDB_PASS;
 
   if (!SURREALDB_URL || !SURREALDB_NAMESPACE || !SURREALDB_DATABASE) {
     throw new Error('SurrealDB configuration is missing');
   }
 
+  if (!SURREALDB_USER || !SURREALDB_PASS) {
+    throw new Error('SurrealDB credentials are missing');
+  }
+
   // Create a new instance for each request to avoid connection state issues
   const db = new Surreal();
 
   // Connect to SurrealDB
   await db.connect(SURREALDB_URL);
 
-  // Authenticate as the user for this request.
-  // This enforces the row-level security (PERMISSIONS)
-  // defined in the schema for all subsequent queries.
-  await db.authenticate(token);
+  // Sign in with root credentials
+  // NOTE: We use root access because our JWT-based auth is app-level,
+  // not SurrealDB-level. Queries must filter by user_did from the verified JWT.
+  await db.signin({
+    username: SURREALDB_USER,
+    password: SURREALDB_PASS,
+  });
 
   // Use the correct namespace and database
   await db.use({