feat(notifications): add ntfy as a first-class notification channel

Adds ntfy.sh (and self-hosted instances) as a new push notification
channel with full parity to the existing webhook channel.

- Backend: NtfyConfig type, getUserNtfyConfig, getAdminNtfyConfig,
  resolveNtfyUrl, sendNtfy (header-based API with Title/Priority/Tags/
  Click headers), testNtfy, NTFY_EVENT_META (priority + emoji tags per
  event), SSRF guard via existing checkSsrf + createPinnedDispatcher
- notificationPreferencesService: ntfy added to NotifChannel union,
  IMPLEMENTED_COMBOS, getActiveChannels parser, getAvailableChannels,
  ADMIN_GLOBAL_CHANNELS, and AvailableChannels interface
- notificationService: per-user ntfy dispatch after webhook block;
  admin-scoped ntfy via getAdminGlobalPref for version_available events
- Routes: POST /api/notifications/test-ntfy with saved-token fallback
- authService: admin_ntfy_server/topic/token in ADMIN_SETTINGS_KEYS,
  masked + encrypted on read/write
- settingsService: ntfy_token added to ENCRYPTED_SETTING_KEYS
- Frontend: ntfy topic/server/token inputs + Save/Test/Clear buttons in
  NotificationsTab; admin Ntfy panel in AdminPage; testNtfy API method
- i18n: full English strings; English placeholders in 14 other locales
- Tests: resolveNtfyUrl, sendNtfy, dispatch integration, UI tests,
  MSW handler for test-ntfy endpoint

server/tests/unit/services/notificationService.test.ts

@@ -458,3 +458,72 @@ describe('send() — channel failure resilience', () => {
     expect(countAllNotifications()).toBe(1);
   });
 });
+
+// ── Ntfy dispatch ─────────────────────────────────────────────────────────────
+
+function setUserNtfyTopic(userId: number, topic = 'my-trek-topic'): void {
+  testDb.prepare("INSERT OR REPLACE INTO settings (user_id, key, value) VALUES (?, 'ntfy_topic', ?)").run(userId, topic);
+}
+
+function setAdminNtfyTopic(topic = 'trek-admin-alerts'): void {
+  setAppSetting(testDb, 'admin_ntfy_topic', topic);
+}
+
+describe('send() — ntfy channel dispatch', () => {
+  beforeEach(() => {
+    fetchMock.mockResolvedValue({ ok: true, text: async () => '' });
+  });
+
+  it('NTFY-SVCB-001 — ntfy fires when channel active and user has topic configured', async () => {
+    const { user } = createUser(testDb);
+    setUserNtfyTopic(user.id);
+    setNotificationChannels(testDb, 'ntfy');
+    const tripId = (testDb.prepare('INSERT INTO trips (title, user_id) VALUES (?, ?)').run('Tokyo', user.id)).lastInsertRowid as number;
+
+    await send({ event: 'trip_invite', actorId: null, scope: 'user', targetId: user.id, params: { trip: 'Tokyo', actor: 'Alice', invitee: 'Bob', tripId: String(tripId) } });
+
+    const ntfyCalls = fetchMock.mock.calls.filter(([url]: [string]) => url.includes('ntfy.sh'));
+    expect(ntfyCalls.length).toBeGreaterThan(0);
+    // Header-based API: metadata in headers, body = plain text
+    expect(ntfyCalls[0][1].headers['Priority']).toBe('4'); // trip_invite = high priority
+    expect(ntfyCalls[0][1].headers['Tags']).toContain('loudspeaker');
+  });
+
+  it('NTFY-SVCB-002 — ntfy skips when channel not in active channels', async () => {
+    const { user } = createUser(testDb);
+    setUserNtfyTopic(user.id);
+    setNotificationChannels(testDb, 'none');
+
+    fetchMock.mockClear();
+    await send({ event: 'trip_invite', actorId: null, scope: 'user', targetId: user.id, params: { trip: 'Paris', actor: 'Alice', invitee: 'Bob', tripId: '1' } });
+
+    const ntfyCalls = fetchMock.mock.calls.filter(([url]: [string]) => url.includes('ntfy.sh'));
+    expect(ntfyCalls.length).toBe(0);
+  });
+
+  it('NTFY-SVCB-003 — ntfy skips when user has no topic configured', async () => {
+    const { user } = createUser(testDb);
+    setNotificationChannels(testDb, 'ntfy');
+    // No ntfy_topic set, but no admin_ntfy_server either — resolveNtfyUrl returns null
+
+    fetchMock.mockClear();
+    await send({ event: 'trip_invite', actorId: null, scope: 'user', targetId: user.id, params: { trip: 'Rome', actor: 'Alice', invitee: 'Bob', tripId: '1' } });
+
+    const ntfyCalls = fetchMock.mock.calls.filter(([url]: [string]) => url.includes('ntfy.sh'));
+    expect(ntfyCalls.length).toBe(0);
+  });
+
+  it('NTFY-SVCB-004 — admin-scoped version_available fires admin ntfy topic', async () => {
+    createAdmin(testDb);
+    setAdminNtfyTopic();
+    setNotificationChannels(testDb, 'none');
+
+    fetchMock.mockClear();
+    await send({ event: 'version_available', actorId: null, scope: 'admin', targetId: 0, params: { version: '3.0.0' } });
+
+    const ntfyCalls = fetchMock.mock.calls.filter(([url]: [string]) => url.includes('ntfy.sh'));
+    expect(ntfyCalls.length).toBeGreaterThan(0);
+    expect(ntfyCalls[0][1].headers['Priority']).toBe('4'); // version_available = high priority
+    expect(ntfyCalls[0][1].headers['Tags']).toContain('package');
+  });
+});