quiet-hours: configurable time-window schedule

Adds QuietHours config section (start/end as HH:MM local time). The loop's
gatherer checks the window each tick: if now falls within [start, end), the
State.QuietHours flag is set to true regardless of the config fact (which
the voice toggle writes independently). Both sources activate quiet —
schedule AND toggle.

Handles midnight-crossing windows (23:00-08:00). The gate already reads
State.QuietHours for care nudge suppression — no gate change needed.

cmd/mavend/main.go

@@ -78,6 +78,9 @@ func run(args []string) error {
 
 	rules := loop.DefaultRules()
 	gatherer := loop.NewGatherer(st, rules)
+	if cfg.QuietHours != nil {
+		gatherer.SetQuietHours(cfg.QuietHours.Start, cfg.QuietHours.End)
+	}
 
 	// ----- phraser (LLM-backed when configured, Stub floor otherwise) -----
 	var phr phraser.Phraser = phraser.NewStub()