Fix login requiring a pre-existing saved key to work at all

Login previously bailed out with "No API key found" unless a key from a
prior signup already happened to be sitting in this browser's localStorage
— meaning login was completely broken on any new device, browser, or after
clearing storage, regardless of a correct password. /api/login now issues
a real usable key on every successful login; the frontend just saves it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/lib/api.ts

@@ -174,10 +174,10 @@ export const api = {
     req<SignupResult>('/api/signup', { method: 'POST', body: JSON.stringify(body) }),
 
   login: (email: string, password: string) =>
-    req<{ user_id: number; email: string; api_key_prefix: string }>('/api/login', {
-      method: 'POST',
-      body: JSON.stringify({ email, password }),
-    }),
+    req<{ user_id: number; email: string; api_key: string; mcp_connection: { url: string; header: string } }>(
+      '/api/login',
+      { method: 'POST', body: JSON.stringify({ email, password }) },
+    ),
 
   me: (apiKey: string) =>
     req<MeResult>('/api/me', { headers: authHeader(apiKey) }),

src/pages/Login.tsx

@@ -13,15 +13,8 @@ export default function Login() {
     setError('');
     setLoading(true);
     try {
-      const savedKey = session.getKey();
-      if (!savedKey) {
-        setError('No API key found. Please use your API key directly or re-generate it from a previous signup.');
-        setLoading(false);
-        return;
-      }
-      // Verify credentials via /api/login then confirm key works
-      await api.login(form.email, form.password);
-      session.save(savedKey, form.email);
+      const result = await api.login(form.email, form.password);
+      session.save(result.api_key, result.email);
       navigate('/dashboard');
     } catch (err: unknown) {
       setError(err instanceof Error ? err.message : 'Login failed');