Print banner before cobra parsing; route arg errors through ui.Error

Two output-style fixes plus a quiet-mode correction.

Banner: a manual scan of os.Args in CLIEntry decides whether to suppress
the banner (--quiet/-q/--cron), then prints it before cobra parses any
arguments. This makes the banner appear even when cobra rejects bad args
("requires at least 2 arg(s)") and on --help — paths that previously
skipped PersistentPreRun entirely. The cobra-side hook plumbing (sync.Once,
PersistentPreRun, custom HelpFunc) is removed.

Errors: rootCmd.SilenceErrors = true so cobra no longer prints its own
"Error: <msg>" line. Any error returned from Execute() goes through
ui.New(os.Stderr).Error(...), giving the documented "🛑 ERROR: <msg>"
format. A new helper cli.ReportError() formats errors from goroutine
paths that can't return through cobra's normal return chain; every
CLI command's fx-goroutine error path now calls it alongside the
existing structured log.Error so both channels record the failure.

Quiet mode: previously --quiet/--cron swapped Vaultik.UI to io.Discard,
which silenced Warning and Error messages too — contradicting the
documented "suppresses non-error output" semantics. ui.Writer now has
a SetQuiet flag that drops Begin/Complete/Info/Notice/Detail/Progress/
Banner only; Warning and Error always emit.

Also folds in restore.go cleanups the audit flagged: the hardcoded
"WARNING:" prefix on the failed-files block now uses ui.Warning +
ui.Detail, the post-restore "Restored N files" line uses ui.Complete,
and the "No files found to restore" branch emits both log.Warn and
ui.Warning so structured logs continue to capture it under --verbose.

internal/cli/app.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"io"
 	"os"
 	"os/signal"
 	"path/filepath"
@@ -36,15 +35,17 @@ type AppOptions struct {
 }
 
 // setupGlobals records the startup time and, when an output-suppression
-// flag is active, replaces the UI writer with a discarding one so no
-// user-facing output is emitted. The startup banner itself is printed
-// by the root command's PersistentPreRun (see maybePrintBanner).
+// flag is active, marks the UI writer quiet so that Begin/Complete/
+// Info/Notice/Detail/Progress are silenced. Warning and Error are NOT
+// silenced — per the documented convention that --quiet suppresses
+// non-error output only. The startup banner is printed by CLIEntry
+// before cobra parses arguments, gated by the same arg-level check.
 func setupGlobals(lc fx.Lifecycle, g *globals.Globals, v *vaultik.Vaultik, opts log.LogOptions) {
 	lc.Append(fx.Hook{
 		OnStart: func(ctx context.Context) error {
 			g.StartTime = time.Now().UTC()
 			if opts.Cron || opts.Quiet {
-				v.UI = ui.NewWithColor(io.Discard, false)
+				v.UI.SetQuiet(true)
 			}
 			return nil
 		},