fix(core): resolve server-client hydration mismatch in theme provider layout

src/components/profile/UserProfile.tsx

@@ -562,10 +562,11 @@ export default function UserProfile() {
                   {(() => {
                     if (!user.createdAt) return 'Dec 2023';
                     try {
+                      const createdAt = user.createdAt as any;
                       const d = new Date(
-                        (user.createdAt as any).seconds
-                          ? (user.createdAt as any).seconds * 1000
-                          : (user.createdAt as any)
+                        createdAt.seconds
+                          ? createdAt.seconds * 1000
+                          : createdAt
                       );
                       if (isNaN(d.getTime())) return 'Dec 2023';
                       return d.toLocaleDateString(undefined, {

src/components/providers/theme-provider.tsx

@@ -22,6 +22,16 @@ function ThemeStoreBridge() {
 }
 
 export function ThemeProvider({ children, ...props }: ThemeProviderProps) {
+  const [mounted, setMounted] = React.useState(false);
+
+  React.useEffect(() => {
+    setMounted(true);
+  }, []);
+
+  if (!mounted) {
+    return <div style={{ visibility: 'hidden' }}>{children}</div>;
+  }
+
   return (
     <NextThemesProvider {...props}>
       <ThemeStoreBridge />

src/context/AuthContext.tsx

@@ -246,7 +246,7 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
                   email: firebaseUser.email,
                   name: firebaseUser.displayName || '',
                   photoURL: firebaseUser.photoURL || '',
-                  role: 'member',
+                  role: 'member' as const,
                   points: 0,
                   streak: 0,
                   level: 0,
@@ -267,7 +267,7 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
                     showInCommunity: true,
                   },
                   preferences: {
-                    theme: 'dark',
+                    theme: 'dark' as const,
                   },
                   githubStats: {
                     connected: false,