feat(auth): Integrate Cloudflare Turnstile bot protection and enhance swarm tracking

- Add Cloudflare Turnstile integration for login and registration forms
- Create turnstile verification utility with server-side token validation
- Add turnstile_site_key and turnstile_secret_key fields to nodes table
- Implement admin panel UI for configuring Turnstile keys in settings
- Update login and register API routes to verify Turnstile tokens
- Expose turnstile_site_key via GET /api/node endpoint for frontend
- Add admin endpoint to save and update Turnstile configuration
- Create remote_likes and remote_reposts tables for federated interaction tracking
- Add swarm reply metadata fields (swarm_reply_to_id, swarm_reply_to_content, swarm_reply_to_author) to posts table
- Add comprehensive TURNSTILE_SETUP.md documentation with setup instructions and security notes
- Create database migration 0007 with schema updates and indexes
- Protects against bot registrations and automated attacks on federated nodes

src/app/api/node/route.ts

@@ -38,10 +38,16 @@ export async function GET() {
                 accentColor: process.env.NEXT_PUBLIC_ACCENT_COLOR || '#FFFFFF',
                 domain,
                 admins,
+                turnstileSiteKey: null,
             });
         }
 
-        return NextResponse.json({ ...node, admins });
+        return NextResponse.json({ 
+            ...node, 
+            admins,
+            // Don't expose the secret key
+            turnstileSecretKey: undefined,
+        });
     } catch (error) {
         console.error('Node info error:', error);
         return NextResponse.json({