feat(engagement): the in-app channel, core and web (engagement Phase 7)

ENGAGEMENT.md Phase 7. `user_notifications`, the in-app DeliveryChannel, the
four inbox routes, and the web surface — plus the two pieces earlier phases
assigned here that Phase 7's own acceptance line omits.

Four decisions settled by the org lead before any code:

1. `inapp` defaults to `instant` — the only channel that does. Push wakes a
   device somebody is holding and email leaves the building, so both are asked
   for; an inbox item is a row on a page the user chose to open. Left `off` the
   channel ships dead.
2. The phase takes push's `deliver` (§2603) and the web per-channel preferences
   screen (Phase 3's as-built), neither of which its own bullets mention.
3. The inbox takes `/auth/me/notifications` and `/account/notifications`; the
   preferences screen moves to `…/settings`. The plain word belongs to the
   content, which is what the bell opens.
4. `ctx.inbox.push` honours the user's in-app preference when `triggerId` names
   a registered trigger, and writes when it does not.

Server
- `user_notifications` + `model/userNotifications/`. The dedupe UNIQUE is scoped
  to the USER, narrower than the outbox's `(rule, user, channel)`: an inbox has
  no channel dimension, so two rows for one event would be one item shown twice.
- `engagement/inappChannel.js` — renders by block ROLE (first heading → title,
  first button → url, the rest → body) and inserts. `pushChannel.js` — a
  content-free `{stream, ref}` tickle whose ref deep-links the inbox row.
- `engine.liveChannels` orders `inapp` first (`CHANNEL_ORDER`) so that ref
  resolves on the first sweep. An ordering, not a dependency.
- `templates.renderInappByKey` + `resolveTemplate` extracted from `renderByKey`,
  so both channels take the same fallback chain.
- `inapp.event` seed → seedVersion 2: it named `body`/`url`, which nothing
  supplies. Renamed to the structural vocabulary the projection fills in.
- `utils/userNotificationsPrune.js` — nightly, READ items only, horizon in
  `settings.user_notifications_retain_days` (default 90).
- `GET /auth/me/notifications`, `…/unread-count`, `POST …/:id/read`,
  `POST …/read-all`. Swagger + route manifest + four component schemas.

Web
- `NotificationBell` in all three headers, polling its badge once a minute and
  pausing while the tab is hidden. `PlayerInbox` at `/account/notifications`.
- The preferences screen becomes a channel matrix over
  `/auth/me/notifications/channels` — a strict superset of the push-only stream
  list it replaces. The two legacy endpoints are untouched, so the shipped
  Android app keeps its wire shape.
- Staff get the same two screens at `/admin/notifications…`: `RequirePlayer`
  keeps them out of `/account`, so without this the inbox was unreachable for
  every non-player account. `lib/notificationPaths.js` is the one mapping.

Verified: 28 new server tests (5 of them against a real MariaDB, for the three
index/statement properties that are a server contract rather than a reading of
this code) + 3 client. Server suite green, client 327 green. A live rig walked
the whole path: two rules on one event produced three outbox rows and exactly
one inbox item, the tickle carried `ref: notification:2`, and the retention
sweep dropped an aged read row while keeping an equally aged unread one.

Docs: RunicGateway/docs#TBD, RunicGateway/runicgateway.com#TBD

Co-Authored-By: Claude <noreply@anthropic.com>

server/src/modules/loader.js

@@ -122,6 +122,7 @@ function buildCtx(id, moduleRoot) {
   const teams = require('../model/teams/teamSync.model')
   const teamActivity = require('../model/teams/teamActivity.model')
   const engagementEmit = require('../utils/engagementEmit')
+  const inappChannel = require('../engagement/inappChannel')
   const { makeLimiter, accountChangeLimiter } = require('../middleware/rateLimit')
   /* eslint-enable global-require */
 
@@ -229,17 +230,26 @@ function buildCtx(id, moduleRoot) {
       },
     },
     // The in-app sink (§5.1) — a module writing the inbox directly, without a
-    // rule. It is PRESENT AND THROWS until Phase 7 builds the channel and the
-    // `user_notifications` table behind it.
+    // rule. Live from Phase 7; it threw until the `user_notifications` table
+    // behind it existed.
     //
-    // Present-and-throwing rather than absent is the shape 1.6.0 settled on for
-    // exactly this situation (`ctx.teams.activity.push` before its phase landed):
-    // the version number states a whole surface, so a member of 1.7.0 that is
-    // missing would make the version a lie, and one that silently accepted data
-    // into a table that does not exist would be the worst of the three.
+    // Fire-and-forget and returns undefined, like `events.emit` above and
+    // `teams.activity.push` before it, and for the same reason: a module calls
+    // this from inside a game-event handler, and there is nothing it could
+    // correctly do with a storage failure of core's. The decision the sink makes
+    // that a module might want to know about — the user has this switched off —
+    // is deliberately not reported either, because a module that could see it
+    // would be a module that could enumerate people's preferences one write at a
+    // time.
+    //
+    // `id` is bound here and never taken from the arguments, exactly as `emit`
+    // and `teams.activity.push` bind theirs.
     inbox: {
-      push: () => {
-        throw new Error('ctx.inbox.push is not available until the in-app channel lands (ENGAGEMENT.md Phase 7)')
+      push: (userId, item) => {
+        inappChannel.pushDirect(id, userId, item).then(
+          (result) => { void result },
+          (err) => { log.error('ctx.inbox.push failed', { module: id, message: err.message }) },
+        )
       },
     },
     // One function, for one caller: the `admin.users.detail` slot router needs