feat: add invite code system and multi-image Drone pipeline

- Add InviteCode model with code, maxUses, expiry, usage tracking
- Registration now requires a valid invite code
- New users get USER role instead of ADMIN
- Admin-only /invites page to create, manage, and share invite codes
- Invite links auto-fill code via ?code= URL param
- Drone pipeline now builds app, worker, and bot images separately
- Add NEXT_PUBLIC_APP_URL build arg to fix URL redirects

src/schemas/auth.schema.ts

@@ -11,6 +11,7 @@ export const registerSchema = z
     email: z.email("Invalid email address"),
     password: z.string().min(6, "Password must be at least 6 characters"),
     confirmPassword: z.string(),
+    inviteCode: z.string().min(1, "Invite code is required"),
   })
   .refine((data) => data.password === data.confirmPassword, {
     message: "Passwords do not match",