mini: note mini.options and Docker filer.toml pitfalls in help (#11755)

* mini: note mini.options and Docker filer.toml pitfalls in help

Two behaviors of "weed mini" surprise users and are not mentioned in
its help text.

Flags are saved to <dir>/mini.options and applied again on the next
start to every flag that still has its default value. Removing a flag,
or passing it with its default value, therefore keeps the saved value.

The official Docker image ships /etc/seaweedfs/filer.toml, which sets
the leveldb2 store to /data/filerldb2. When filer.toml is found, the
filer ignores the default store dir derived from -dir, so moving -dir
away from /data leaves the metadata in /data. If /data is not
persisted, buckets look empty after the container is recreated.

Only the help text changes.

Signed-off-by: YoungjuKim <fjvbn2003@gmail.com>

* mini: update help notes for computed-only mini.options

---------

Signed-off-by: YoungjuKim <fjvbn2003@gmail.com>
Co-authored-by: Chris Lu <chris.lu@gmail.com>

weed/command/mini.go

@@ -378,6 +378,19 @@ The S3 endpoint is available at http://localhost:8333. For client
 configuration and IAM setup, see the project documentation or use the
 Admin UI (http://localhost:23646) to manage users and policies.
 
+Notes:
+- Values mini computes itself (currently master.volumeSizeLimitMB) are
+  pinned in <dir>/mini.options and applied again on the next start to
+  keep them stable; applied values are printed at startup. Command-line
+  flags are never saved and always win over saved values. Edit or
+  delete mini.options to reset a computed value.
+- The official Docker image ships /etc/seaweedfs/filer.toml, which keeps
+  the filer metadata in /data/filerldb2 regardless of -dir; mini warns
+  at startup when a configured store dir is outside -dir. If you set
+  -dir to another path, keep /data on a persistent volume as well.
+  Otherwise the metadata is lost when the container is recreated, and
+  buckets list no objects although the volume files are still in -dir.
+
 `,
 }