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/log.go

@@ -35,6 +35,7 @@ type Config struct {
 	Verbose bool
 	Debug   bool
 	Cron    bool
+	Quiet   bool
 }
 
 var logger *slog.Logger
@@ -44,8 +45,8 @@ func Initialize(cfg Config) {
 	// Determine log level based on configuration
 	var level slog.Level
 
-	if cfg.Cron {
-		// In cron mode, only show fatal errors (which we'll handle specially)
+	if cfg.Cron || cfg.Quiet {
+		// In quiet/cron mode, only show errors
 		level = slog.LevelError
 	} else if cfg.Debug || strings.Contains(os.Getenv("GODEBUG"), "vaultik") {
 		level = slog.LevelDebug

internal/log/module.go

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