feat(notifications): Phase C — Don't Disturb (quiet hours window)

User задаёт quiet window (e.g. 22:00–08:00 Europe/Moscow) — external
channels (email + express) DROP'аются dispatcher'ом. In-app bell badge
остаётся (юзер видит при следующем визите UI). Cross-midnight aware.

## Backend

- Migration 0026: user_notification_settings table (user_id PK + quiet_hours_start/end LocalTime + tz)
- Entity UserNotificationSettings + Repository (stock CRUD)
- UserPreferencesGate extended:
  - Constructor takes settingsRepo
  - allows() checks isQuiet(userId) первым for external channels (EMAIL/EXPRESS/TELEGRAM)
  - isQuiet: load settings → if hasEffectiveQuietHours() → check current LocalTime в user's TZ
  - inWindow() helper: cross-midnight semantics (22:00–08:00 wraps midnight)
  - Invalid TZ → fallback к DEFAULT_TZ (Europe/Moscow) с WARN log
  - Test seam: setClockForTesting(Clock) для deterministic tests
- MeNotificationsSettingsController: GET/PUT /api/v1/me/notifications/settings
  - HH:mm input parsing, IANA TZ validation, enabled=false clears window
  - Auth required (JWT sub claim)

## Frontend

- NotificationSettings type в client.ts
- useMyNotificationSettings query (60s stale)
- useUpdateNotificationSettings mutation
- QuietHoursSection в /me/notifications/preferences route:
  - Switch toggle + 2 time inputs + TZ select (12 RU/UTC zones)
  - Optimistic local state synced from query
  - Save button с pending/success/error states
- i18n RU + EN

## Tests

- 9 new tests UserPreferencesGateQuietHoursTest:
  - Same-day window match (inclusive start, exclusive end)
  - Cross-midnight window match (22:00–08:00)
  - No settings row → не блокирует
  - Quiet window active → email + express dropped
  - Outside window → email allowed
  - start == end → disabled (zero-duration treated as off)
  - Reviewer pool bypasses (always ON)
  - Invalid TZ → fallback default
  - Specific pref ON + quiet ON → quiet wins (drop)
- NotificationsDispatcherTest constructor updated к new signature
- Total notifications tests: 53 → 62, все green

## Design rationale (drop vs defer)

Drop chosen за defer (queue + re-fire scheduler) потому что:
- Defer needs persistent queue + scheduled retry — high complexity
- Most notifications time-relevant (draft N hours ago less actionable)
- Bell badge показывает full feed — ничего не «теряется»
- Phase D summary digest можно build later если demand surfaces

ordinis-admin-ui/src/api/client.ts

@@ -764,6 +764,18 @@ export type ChannelToggles = {
 /** Map keyed по event type. Backend сейчас возвращает 4 known events. */
 export type NotificationPreferences = Record<string, ChannelToggles>
 
+/**
+ * Phase C Don't Disturb — per-user quiet hours. Когда window активен,
+ * external channels (email + express) DROPPED dispatcher'ом. Bell badge
+ * остаётся.
+ */
+export type NotificationSettings = {
+  quietHoursEnabled: boolean
+  quietHoursStart: string | null   // "HH:mm" or "HH:mm:ss"
+  quietHoursEnd: string | null
+  quietHoursTz: string             // IANA, default "Europe/Moscow"
+}
+
 /**
  * Canonical event types — должны совпадать с backend
  * MeNotificationsPreferencesController.KNOWN_EVENT_TYPES.