feat(docker): default CMD to mini -dir=/data for service-container use (#9255)

* feat(docker): default CMD to `mini -dir=/data` for service-container use

GitHub Actions service containers cannot pass arguments to the image
entrypoint, so `chrislusf/seaweedfs` is currently unusable as a service
because it requires a `weed` subcommand. Set a sensible default CMD so
the image starts a complete single-process cluster (master, volume,
filer, S3 on :8333, admin UI) out of the box, while still being
overridable by passing any other subcommand at `docker run` /
compose time.

Also add a `mini` case to entrypoint.sh so its logs go to stderr,
matching the existing master/volume/server cases.

Closes #9247

* fix(docker): make `isArgPassed` match `--flag` as well as `-flag`

The Go fla9 library accepts both `-flag` and `--flag` syntax, but
`isArgPassed` only matched the single-dash form. That meant a user
passing `--dir=/foo` to `weed mini` (or `--max=5` to `volume`,
`--volume.max=5` to `server`) would not suppress the entrypoint's
default, and the duplicate flag was silently appended to the command
line — relying on last-wins parsing for correctness. Match double-dash
explicitly so the override is detected for every case in the file.

docker/Dockerfile.local

@@ -40,3 +40,8 @@ WORKDIR /data
 
 # Entrypoint will handle permission fixes and user switching
 ENTRYPOINT ["/entrypoint.sh"]
+# Default to a complete single-process cluster (master+volume+filer+S3+admin)
+# so the image is usable out of the box — including in environments like
+# GitHub Actions service containers that cannot pass arguments to the entrypoint.
+# Override with any other subcommand at `docker run` / compose time.
+CMD ["mini", "-dir=/data"]