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.

server/package.json

@@ -26,12 +26,13 @@
     "jsonwebtoken": "^9.0.2",
     "multer": "^2.1.1",
     "node-cron": "^4.2.1",
-    "undici": "^7.0.0",
     "nodemailer": "^8.0.5",
     "otplib": "^12.0.1",
     "qrcode": "^1.5.4",
+    "semver": "^7.7.4",
     "tsx": "^4.21.0",
     "typescript": "^6.0.2",
+    "undici": "^7.0.0",
     "unzipper": "^0.12.3",
     "uuid": "^9.0.0",
     "ws": "^8.19.0",
@@ -54,6 +55,7 @@
     "@types/node-cron": "^3.0.11",
     "@types/nodemailer": "^7.0.11",
     "@types/qrcode": "^1.5.5",
+    "@types/semver": "^7.7.1",
     "@types/supertest": "^6.0.3",
     "@types/unzipper": "^0.10.11",
     "@types/uuid": "^10.0.0",