feat(tracking): per-config quiet hours with app-level IANA timezone

Add quiet_hours_enabled/start/end to TrackingConfig (HH:MM strings
interpreted in the app-level timezone AppSetting). The dispatch path
loads the app timezone once per run and passes it through
event_allowed_by_config -> in_quiet_hours, so overnight windows like
22:00-07:00 work correctly in any IANA tz.

Frontend exposes a Timezone field under Settings and a Quiet Hours
section on the Immich tracking-config form with time-picker inputs.

frontend/src/routes/settings/+page.svelte

@@ -19,6 +19,7 @@
 		telegram_webhook_secret: '',
 		telegram_cache_ttl_hours: '48',
 		supported_locales: 'en,ru',
+		timezone: 'UTC',
 	});
 
 	onMount(async () => {
@@ -57,6 +58,11 @@
 					<input bind:value={settings.external_url} placeholder="https://notify.example.com"
 						class="w-full max-w-md px-3 py-1.5 text-sm border border-[var(--color-border)] rounded-md bg-[var(--color-background)] font-mono" />
 				</div>
+				<div>
+					<label class="block text-xs font-medium mb-1">{t('settings.timezone')}<Hint text={t('settings.timezoneHint')} /></label>
+					<input bind:value={settings.timezone} placeholder="UTC"
+						class="w-full max-w-md px-3 py-1.5 text-sm border border-[var(--color-border)] rounded-md bg-[var(--color-background)] font-mono" />
+				</div>
 			</div>
 		</Card>