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-domain/src/main/java/cloud/nstart/terravault/ordinis/domain/notification/UserNotificationSettings.java

@@ -0,0 +1,109 @@
+package cloud.nstart.terravault.ordinis.domain.notification;
+
+import jakarta.persistence.Column;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.PrePersist;
+import jakarta.persistence.PreUpdate;
+import jakarta.persistence.Table;
+
+import java.time.LocalTime;
+import java.time.OffsetDateTime;
+
+/**
+ * Per-user global notification settings (Phase C Don't Disturb).
+ *
+ * <p>Хранит one quiet hours window per user (start/end LocalTime + IANA TZ).
+ * Если оба start и end null OR равны — quiet hours disabled (no muting).
+ *
+ * <p>Cross-midnight ranges OK: window {@code 22:00–08:00} активен когда
+ * текущий момент в зоне попадает либо в {@code [22:00, 23:59:59]}, либо в
+ * {@code [00:00, 08:00)}. Resolved в {@code UserPreferencesGate#isQuiet}.
+ *
+ * <p>Применяется только к external channels (email + express). In-app bell
+ * badge остаётся (юзер всё равно видит при следующем визите).
+ *
+ * <p>В отличие от {@link UserNotificationPref} (per event×channel matrix)
+ * это global per-user setting — отдельная таблица чище чем denormalize
+ * в каждую prefs row.
+ */
+@Entity
+@Table(name = "user_notification_settings")
+public class UserNotificationSettings {
+
+  /** Default IANA timezone когда user не указал. */
+  public static final String DEFAULT_TZ = "Europe/Moscow";
+
+  @Id
+  @Column(name = "user_id", length = 128, nullable = false)
+  private String userId;
+
+  /** NULL → quiet hours disabled. */
+  @Column(name = "quiet_hours_start")
+  private LocalTime quietHoursStart;
+
+  @Column(name = "quiet_hours_end")
+  private LocalTime quietHoursEnd;
+
+  @Column(name = "quiet_hours_tz", length = 64)
+  private String quietHoursTz;
+
+  @Column(name = "created_at", nullable = false, updatable = false)
+  private OffsetDateTime createdAt;
+
+  @Column(name = "updated_at", nullable = false)
+  private OffsetDateTime updatedAt;
+
+  protected UserNotificationSettings() {}
+
+  public UserNotificationSettings(String userId) {
+    this.userId = userId;
+  }
+
+  @PrePersist
+  void onCreate() {
+    OffsetDateTime now = OffsetDateTime.now();
+    if (createdAt == null) createdAt = now;
+    updatedAt = now;
+  }
+
+  @PreUpdate
+  void onUpdate() {
+    updatedAt = OffsetDateTime.now();
+  }
+
+  public String getUserId() { return userId; }
+  public LocalTime getQuietHoursStart() { return quietHoursStart; }
+  public LocalTime getQuietHoursEnd() { return quietHoursEnd; }
+  public String getQuietHoursTz() { return quietHoursTz; }
+  public OffsetDateTime getCreatedAt() { return createdAt; }
+  public OffsetDateTime getUpdatedAt() { return updatedAt; }
+
+  public void setQuietHoursStart(LocalTime quietHoursStart) {
+    this.quietHoursStart = quietHoursStart;
+  }
+
+  public void setQuietHoursEnd(LocalTime quietHoursEnd) {
+    this.quietHoursEnd = quietHoursEnd;
+  }
+
+  public void setQuietHoursTz(String quietHoursTz) {
+    this.quietHoursTz = quietHoursTz;
+  }
+
+  /**
+   * True если quiet hours effective (both bounds set, not equal).
+   * Equal start==end treated as disabled (zero-duration window — likely user
+   * confusion vs intent).
+   */
+  public boolean hasEffectiveQuietHours() {
+    return quietHoursStart != null
+        && quietHoursEnd != null
+        && !quietHoursStart.equals(quietHoursEnd);
+  }
+
+  /** Effective TZ ID для resolution — fallback к DEFAULT_TZ. */
+  public String effectiveTz() {
+    return (quietHoursTz == null || quietHoursTz.isBlank()) ? DEFAULT_TZ : quietHoursTz;
+  }
+}

ordinis-domain/src/main/java/cloud/nstart/terravault/ordinis/domain/notification/UserNotificationSettingsRepository.java

@@ -0,0 +1,14 @@
+package cloud.nstart.terravault.ordinis.domain.notification;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+
+/**
+ * Repository для per-user global notification settings (Phase C Don't Disturb).
+ *
+ * <p>Single-row-per-user table — все queries via PK lookup {@code findById(userId)}.
+ * Inherits stock CRUD methods из {@link JpaRepository}, custom queries
+ * не нужны на этой фазе.
+ */
+public interface UserNotificationSettingsRepository
+    extends JpaRepository<UserNotificationSettings, String> {
+}