Merge watch profiles into user accounts — one profile per login, no picker

- Removed the "Who's Watching" sub-profile picker entirely: ProfileProvider now
  auto-resolves the single profile tied to the account immediately after login
- Backend: removed POST/DELETE /profiles (no more creating/deleting extra
  profiles — lifecycle is entirely driven by user create/delete, already wired
  in the admin Users CRUD); kept GET (internal) and PATCH (edit your own
  profile's avatar/kids-mode/rating cap)
- Deleted ProfileSelect page and the now-unused ProtectedRoute component
- Navbar: removed the "switch profile" action, account avatar is now just a
  static display
- api.js: dropped the now-dead X-Profile-Id header logic (backend already
  falls back to the account's single profile when the header is absent)

frontend/src/lib/profile.jsx

@@ -6,19 +6,15 @@ const ProfileCtx = createContext(null);
 
 export const ProfileProvider = ({ children }) => {
   const { user } = useAuth();
-  const [profiles, setProfiles] = useState([]);
   const [active, setActive] = useState(null);
   const [loading, setLoading] = useState(false);
 
   const refresh = useCallback(async () => {
-    if (!user) { setProfiles([]); setActive(null); return; }
+    if (!user) { setActive(null); return; }
     setLoading(true);
     try {
       const { data } = await api.get("/profiles");
-      setProfiles(data);
-      const stored = localStorage.getItem(`kino_profile_${user.id}`);
-      const found = data.find((p) => p.id === stored);
-      setActive(found || null);
+      setActive(data[0] || null);
     } finally {
       setLoading(false);
     }
@@ -26,20 +22,8 @@ export const ProfileProvider = ({ children }) => {
 
   useEffect(() => { refresh(); }, [refresh]);
 
-  const switchTo = (p) => {
-    if (!user) return;
-    localStorage.setItem(`kino_profile_${user.id}`, p.id);
-    setActive(p);
-  };
-
-  const clearActive = () => {
-    if (!user) return;
-    localStorage.removeItem(`kino_profile_${user.id}`);
-    setActive(null);
-  };
-
   return (
-    <ProfileCtx.Provider value={{ profiles, active, loading, refresh, switchTo, clearActive }}>
+    <ProfileCtx.Provider value={{ active, loading, refresh }}>
       {children}
     </ProfileCtx.Provider>
   );