feat(notices): add system notice infrastructure

Server-side notice registry with per-user condition evaluation (firstLogin,
existingUserBeforeVersion, addonEnabled, dateWindow, role, custom).
Notices are sorted by priority then severity, filtered against dismissals
stored in a new user_notice_dismissals table, and served via
GET /api/system-notices/active + POST /api/system-notices/:id/dismiss.

Client renders notices through a host component that partitions by
display type (modal / banner / toast). The modal renderer supports
multi-page pagination with directional slide transitions, keyboard
navigation, and correct dismiss-all semantics on CTA / X / ESC.
Dismissals are optimistic with a single background retry.

Includes 3.0.0 upgrade notices (v3-photos, v3-journey, v3-features),
onboarding welcome modal, and full i18n coverage across 15 languages.
The /journey route is addon-gated on both client and server.

Also includes: unit + integration test suites, registry integrity test
that validates action CTA IDs against client source, and technical
documentation in docs/system-notices.md.

client/src/store/authStore.ts

@@ -6,6 +6,7 @@ import type { User } from '../types'
 import { getApiErrorMessage } from '../types'
 import { tripSyncManager } from '../sync/tripSyncManager'
 import { clearAll } from '../db/offlineDb'
+import { useSystemNoticeStore } from './systemNoticeStore.js'
 
 interface AuthResponse {
   user: User
@@ -91,6 +92,9 @@ export const useAuthStore = create<AuthState>()(
       })
       connect()
       tripSyncManager.syncAll().catch(console.error)
+      if (!data.user?.must_change_password) {
+        useSystemNoticeStore.getState().fetch()
+      }
       return data as AuthResponse
     } catch (err: unknown) {
       const error = getApiErrorMessage(err, 'Login failed')
@@ -112,6 +116,9 @@ export const useAuthStore = create<AuthState>()(
       })
       connect()
       tripSyncManager.syncAll().catch(console.error)
+      if (!data.user?.must_change_password) {
+        useSystemNoticeStore.getState().fetch()
+      }
       return data as AuthResponse
     } catch (err: unknown) {
       const error = getApiErrorMessage(err, 'Verification failed')
@@ -133,6 +140,7 @@ export const useAuthStore = create<AuthState>()(
       })
       connect()
       tripSyncManager.syncAll().catch(console.error)
+      useSystemNoticeStore.getState().fetch()
       return data
     } catch (err: unknown) {
       const error = getApiErrorMessage(err, 'Registration failed')