Add --quiet flag, --json output, and config permission check

- Add global --quiet/-q flag to suppress non-error output
- Add --json flag to verify, snapshot rm, and prune commands
- Add config file permission check (warns if world/group readable)
- Update TODO.md to remove completed items

internal/log/module.go

@@ -21,4 +21,5 @@ type LogOptions struct {
 	Verbose bool
 	Debug   bool
 	Cron    bool
+	Quiet   bool
 }