Refactor: Extract master template to shared file and add unconfirmed email handling

- Create supabase/shared/email-template-renderer.ts for code reuse
- Update send-auth-otp to import from shared file (eliminates 260 lines of duplication)
- Add isResendOTP state to track existing user email confirmation
- Update login error handler to detect unconfirmed email
- Show helpful message when user tries to login with unconfirmed email

This addresses:
1. Code duplication between src/lib and edge functions
2. User experience for unconfirmed email login attempts

src/pages/Auth.tsx

@@ -22,6 +22,7 @@ export default function Auth() {
   const [loading, setLoading] = useState(false);
   const [pendingUserId, setPendingUserId] = useState<string | null>(null);
   const [resendCountdown, setResendCountdown] = useState(0);
+  const [isResendOTP, setIsResendOTP] = useState(false); // Track if this is resend OTP for existing user
   const { signIn, signUp, user, sendAuthOTP, verifyAuthOTP } = useAuth();
   const navigate = useNavigate();
 
@@ -57,9 +58,26 @@ export default function Auth() {
     if (isLogin) {
       const { error } = await signIn(email, password);
       if (error) {
+        // Check if error is due to unconfirmed email
+        if (error.message.includes('Email not confirmed') || error.message.includes('Email not verified')) {
+          toast({
+            title: 'Email Belum Dikonfirmasi',
+            description: 'Kirim ulang kode verifikasi ke email Anda?',
+            variant: 'destructive'
+          });
+          // Switch to OTP resend flow
+          setIsResendOTP(true);
+          setShowOTP(true);
+          // Get user ID from error or fetch it
+          // For now, we'll handle it in the OTP resend button
+          setLoading(false);
+          return;
+        }
         toast({ title: 'Error', description: error.message, variant: 'destructive' });
+        setLoading(false);
       } else {
         navigate('/dashboard');
+        setLoading(false);
       }
     } else {
       if (!name.trim()) {