Print banner when vaultik is invoked with no subcommand

Cobra's default 'no subcommand → print help' path bypasses fx, so
the startup banner never ran for bare 'vaultik'. Add a Run handler
on the root command that prints the banner and then calls Help.

Extracted the banner-printing logic into writeStartupBanner() so
both this path and the fx setupGlobals hook share one implementation.

internal/cli/app.go

@@ -46,18 +46,25 @@ func setupGlobals(lc fx.Lifecycle, g *globals.Globals, v *vaultik.Vaultik, opts
 				// user-facing output is suppressed.
 				v.UI = ui.NewWithColor(io.Discard, false)
 			} else {
-				v.UI.Banner("%s %s by %s (commit %s, built on %s) starting up at %s.",
-					g.Appname, g.Version, globals.Author,
-					g.ShortCommit(), g.CommitDate,
-					g.StartTime.Format(time.RFC3339))
-				v.UI.Banner("%s", globals.Homepage)
-				v.UI.Banner("")
+				writeStartupBanner(v.UI, g.StartTime, g.ShortCommit())
 			}
 			return nil
 		},
 	})
 }
 
+// writeStartupBanner prints the two-line application banner followed by a
+// blank line. Used both from the fx hook (for subcommand invocations) and
+// from the root cobra Run handler (for `vaultik` with no subcommand).
+func writeStartupBanner(w *ui.Writer, startTime time.Time, shortCommit string) {
+	w.Banner("%s %s by %s (commit %s, built on %s) starting up at %s.",
+		globals.Appname, globals.Version, globals.Author,
+		shortCommit, globals.CommitDate,
+		startTime.Format(time.RFC3339))
+	w.Banner("%s", globals.Homepage)
+	w.Banner("")
+}
+
 // NewApp creates a new fx application with common modules.
 // It sets up the base modules (config, database, logging, globals) and
 // combines them with any additional modules specified in the options.