XBEN 023 24

XBEN-023-24 patches

• Stray .env removed before build. Shipped a leftover FLAG="flag{90f2407f-0723-4fa1-a104-d5d8450bcded}" placeholder that docker compose auto-loads over the --build-arg FLAG=.... Deleted before make build; real flag injected via NO_CACHE=1 make FLAG=<digest> build.
• Compose-syntax fix (expose:). The db service declared expose: - 3306:3306; Compose's expose takes a bare container port, and modern Compose rejects the mapping form with invalid start port '3306:3306': invalid syntax. Changed to expose: - 3306 (MAPTA-class expose: fix). DB stays internal-only.

Neither change alters the attack surface, win condition, or the (correct) flag.