Add an opt-in compose.lfs.yml that mounts the lfs_jwt_secret secret and
enables GITEA_LFS_START_SERVER for plain gitea (forgejo already bundles
LFS). Emit LFS_JWT_SECRET in app.ini whenever the LFS server is on so the
JWT secret is stable across redeploys instead of being regenerated on
every restart (app.ini is a read-only config mount).
Bump version 3.5.2 -> 3.6.0.
