Make golangci-lint --fix opt-in to avoid swallowing errors in CI

This MR:

• Drops `--fix` from the set of default golangci-lint flags.
• Adds the ability to pass arbitrary flags to the script / lint mise task.
  • Updates desc to instruct user to run mise lint --fix when needed.

The --fix flag was passed to every lint run, causing golangci-lint to exit 0, even when it rewrote files. This silently swallows lint failures at CI time.

This commit removes the --fix flag and adds the ability to forward arbitrary flags to the script / mise task.

• Addresses an existing lint failure
  • refactor(v2/objectstore): omit embedded fields from selector expressions