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/web/src/components/modals/UserProfileModal.tsx

@@ -321,6 +321,11 @@ export function UserProfileModal() {
                     <ReactMarkdown
                       allowedElements={['p', 'strong', 'em', 'a', 'br']}
                       unwrapDisallowed
+                      components={{
+                        a: ({ href, children }) => (
+                          <a href={href} target="_blank" rel="noopener noreferrer">{children}</a>
+                        ),
+                      }}
                     >
                       {user.bio}
                     </ReactMarkdown>