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>

client/src/routes/admin/AdminLayout.jsx

@@ -2,6 +2,7 @@ import { useEffect, useMemo, useState } from 'react'
 import { NavLink, Outlet, useNavigate, useLocation } from 'react-router-dom'
 import MoonDot from '../../components/MoonDot.jsx'
 import BrandLogo from '../../components/BrandLogo.jsx'
+import NotificationBell from '../../components/NotificationBell.jsx'
 import { useAuth } from '../../contexts/AuthContext.jsx'
 import { useSite } from '../../contexts/SiteContext.jsx'
 import { applyNavOverrides } from '../../lib/navOverrides.js'
@@ -43,6 +44,7 @@ const IconKey = () => <Icon><circle cx="8" cy="12" r="4" /><path d="M12 12h9M18
 const IconBot = () => <Icon><rect x="4" y="8" width="16" height="11" rx="2" /><path d="M12 8V4M8 13h.01M16 13h.01M9 17h6" /></Icon>
 const IconPulse = () => <Icon><path d="M3 12h3l2 6 4-14 2 8h7" /></Icon>
 const IconUser = () => <Icon><circle cx="12" cy="8" r="4" /><path d="M4 21a8 8 0 0 1 16 0" /></Icon>
+const IconBell = () => <Icon><path d="M18 8a6 6 0 10-12 0c0 7-3 9-3 9h18s-3-2-3-9" /><path d="M13.7 21a2 2 0 01-3.4 0" /></Icon>
 const IconNav = () => <Icon><path d="M4 6h16M4 12h16M4 18h10" /><circle cx="18" cy="18" r="2.5" /></Icon>
 const IconPalette = () => <Icon><path d="M12 3a9 9 0 1 0 0 18 2 2 0 0 0 1.6-3.2 2 2 0 0 1 1.6-3.2H18a3 3 0 0 0 3-3 9 9 0 0 0-9-8.6z" /><circle cx="7.5" cy="11.5" r="1" /><circle cx="10.5" cy="7.5" r="1" /><circle cx="15" cy="8.5" r="1" /></Icon>
 const IconModules = () => <Icon><path d="M12 3l8 4.5-8 4.5-8-4.5z" /><path d="M4 12l8 4.5 8-4.5" /><path d="M4 16.5L12 21l8-4.5" /></Icon>
@@ -129,6 +131,11 @@ export const NAV = [
   },
   {
     items: [
+      // No `end`: `allowedPathsFor` turns an `end` row into an EXACT match, so
+      // marking this one exact would leave `/admin/notifications/settings`
+      // outside the allowlist and bounce a staff member off their own
+      // preferences screen. The row covering its sub-routes is the point.
+      { to: '/admin/notifications', label: 'Notifications', icon: IconBell },
       { to: '/admin/account', label: 'Account', icon: IconUser },
     ],
   },
@@ -177,6 +184,8 @@ const TITLES = {
   '/admin/users': 'Users',
   '/admin/invites': 'Invites',
   '/admin/account': 'Account Security',
+  '/admin/notifications': 'Notifications',
+  '/admin/notifications/settings': 'Notification settings',
   '/admin/engagement/rules': 'Engagement Rules',
   '/admin/engagement/audiences': 'Engagement Audiences',
   '/admin/engagement/templates': 'Message Templates',
@@ -443,6 +452,11 @@ export default function AdminLayout() {
             {title}
           </h1>
           <div className="sans" style={{ display: 'flex', alignItems: 'center', gap: 14, fontSize: '0.84rem', color: 'var(--muted)' }}>
+            {/* Staff have an inbox like anyone else — `/auth/me/notifications`
+                is role-agnostic — and `RequirePlayer` keeps them out of the
+                player portal, so without this the one place they spend their
+                time is the one place the bell is missing. */}
+            <NotificationBell />
             <a href="/" target="_blank" rel="noreferrer" style={{ color: 'var(--accent)', textDecoration: 'none' }}>
               View site →
             </a>