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/engagement/engine.js

@@ -42,6 +42,22 @@ const log = require('../utils/logger')('engagement')
 
 const HOUR_MS = 60 * 60 * 1000
 
+// Channels one of whose payloads can REFERENCE another's result, earliest first
+// (Phase 7). Only one pair qualifies today: a push tickle's `ref` deep-links to
+// the inbox row `inapp` writes, and the outbox is swept `ORDER BY due_at, id`,
+// so enqueueing in-app first is what makes that ref resolve on the first pass
+// rather than on a retry. Everything not named here keeps the operator's own
+// order, which is the order the rules screen shows.
+//
+// It is an ordering, not a dependency: `pushChannel` treats a missing ref as
+// null and the app pulls regardless, so a rule that names only push, or a row
+// that gets retried out of sequence, is still correct.
+const CHANNEL_ORDER = ['inapp']
+const channelRank = (id) => {
+  const i = CHANNEL_ORDER.indexOf(id)
+  return i === -1 ? CHANNEL_ORDER.length : i
+}
+
 /**
  * Which of a rule's channels are actually deliverable right now?
  *
@@ -50,7 +66,10 @@ const HOUR_MS = 60 * 60 * 1000
  * failing the rule: the other channels of that rule are still correct, and a
  * dropped one is visible in the log line below.
  */
-const liveChannels = (rule) => (rule.channels || []).filter((c) => channels.has(c))
+const liveChannels = (rule) =>
+  (rule.channels || [])
+    .filter((c) => channels.has(c))
+    .sort((a, b) => channelRank(a) - channelRank(b))
 
 /**
  * The EFFECTIVE mode each candidate holds for (id, channel), given the event's
@@ -267,4 +286,13 @@ async function dispatch(event, now = new Date()) {
   return summary
 }
 
-module.exports = { dispatch, applyRule, applyCancellations, subscribedTo, effectiveModes, liveChannels, HOUR_MS }
+module.exports = {
+  dispatch,
+  applyRule,
+  applyCancellations,
+  subscribedTo,
+  effectiveModes,
+  liveChannels,
+  CHANNEL_ORDER,
+  HOUR_MS,
+}