feat: security hardening, DB indexes, token revocation, and input validation

- SSRF protection: DNS resolution + private IP blocking on metadata fetcher
- Upload security: CSP/X-Frame-Options headers, SVG forced download, nosniff
- Auth hardening: JWT secret min length, password min 8 chars, token revocation via password_changed_at
- Attachment ownership verification before linking to messages
- Message length limit (4000 chars) enforced on client and server
- Asset URL validation on avatar/banner updates
- Federation instance validation (domain regex, origin scheme, length limits)
- DB indexes on all FK columns for query performance
- Migrations: nullable moderator columns, dm_messages reply_to FK constraint
- File cleanup on avatar/banner replacement and space deletion
- Fastify trustProxy, AbortController on fetches, typing map size cap

packages/server/src/routes/auth.ts

@@ -68,8 +68,8 @@ export async function authRoutes(app: FastifyInstance): Promise<void> {
       }
     }
 
-    if (password.length < 6) {
-      return reply.code(400).send({ error: 'Password must be at least 6 characters', statusCode: 400 });
+    if (password.length < 8) {
+      return reply.code(400).send({ error: 'Password must be at least 8 characters', statusCode: 400 });
     }
 
     const db = getDb();