Migrate authentication to Better Auth

Replace the hand-rolled JWT auth with Better Auth 1.6.25 httpOnly cookie
sessions, validated against the database on every request so revocation,
bans and role changes take effect immediately.

Backend:
- betterAuth.ts wires the Drizzle adapter, magic links, Google sign-in and
  the admin plugin; auth-schema.ts maps Better Auth's models onto the
  existing `users` table so user IDs and their foreign keys survive intact.
- routes/auth.ts is gone; Better Auth serves the standard endpoints and
  authExt.ts carries the flows it doesn't cover.
- auth.ts shrinks to session resolution and helpers; sessions/revocation in
  dashboard.ts now read and delete `auth_sessions` rows directly.
- Schema adds the Better Auth core + admin columns (email_verified, image,
  banned, ban_reason, ban_expires), with migrations and tests.
- rateLimit.ts resolves client IPs spoof-resistantly: proxy headers are only
  honoured from loopback/RFC1918 peers plus TRUSTED_PROXIES.
- passwordPolicy.ts centralises password validation.
- Bump drizzle-orm, drizzle-kit and better-sqlite3 to versions compatible
  with Better Auth.

Frontend:
- auth-client.ts plus a reworked AuthContext and api/client.ts move to
  cookie-based sessions; no more bearer tokens in requests or middleware.

photo-api:
- Validate Better Auth session cookies against the shared auth_sessions
  table instead of verifying JWTs; JWT_SECRET is no longer needed for user
  auth, and PHOTO_VIEW_SECRET now signs gallery view tokens.

BETTER_AUTH_SECRET and BETTER_AUTH_URL are required in production; the
deprecated JWT_SECRET stays only as the photo-api view-token fallback.

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

frontend/src/app/(public)/auth/magic-link/page.tsx

@@ -6,6 +6,7 @@ import { useLanguage } from '@/context/LanguageContext';
 import { useAuth } from '@/context/AuthContext';
 import Card from '@/components/ui/Card';
 import Button from '@/components/ui/Button';
+import { safeInternalPath } from '@/lib/safeRedirect';
 import toast from 'react-hot-toast';
 
 function MagicLinkContent() {
@@ -18,11 +19,12 @@ function MagicLinkContent() {
   const verificationAttempted = useRef(false);
 
   const token = searchParams.get('token');
+  const callbackURL = safeInternalPath(searchParams.get('callbackURL'), '/dashboard');
 
   useEffect(() => {
     // Prevent duplicate verification attempts (React StrictMode double-invokes effects)
     if (verificationAttempted.current) return;
-    
+
     if (token) {
       verificationAttempted.current = true;
       verifyToken();
@@ -34,11 +36,17 @@ function MagicLinkContent() {
 
   const verifyToken = async () => {
     try {
-      await loginWithMagicLink(token!);
+      const user = await loginWithMagicLink(token!);
       setStatus('success');
       toast.success(language === 'es' ? '¡Bienvenido!' : 'Welcome!');
+      // Unclaimed accounts must finish the claim (set a password) before the
+      // rest of the API will accept their session.
+      const destination =
+        user && (user.isClaimed === false || user.accountStatus === 'unclaimed')
+          ? '/auth/claim-account'
+          : callbackURL;
       setTimeout(() => {
-        router.push('/dashboard');
+        router.push(destination);
       }, 1500);
     } catch (err: any) {
       setStatus('error');