Support inbox drawer on the topbar, 1:1 with the notification drawer (#45)

## Summary

A Support inbox drawer on the topbar, next to the notification bell, fed by
the plugin-owned support inbox in sow-nodebb-plugin-support#15.

It is not a lookalike: the rows are rendered with core's own
`partials/notifications_list` partial, from entries the support plugin now
returns in core's notification field names, inside a dropdown that copies
Harmony's `partials/sidebar/notifications.tpl`. So the drawer has the
notification drawer's avatar block, stretched link, muted timeago, per-entry
read dot, All/Unread filter row, and the same two footer buttons — and needs
no CSS of its own, because it reuses the `.notifications-dropdown` classes
this theme already styles.

Behaviour matches the bell too: opening the box does not mark anything read;
an entry is read when you click it or use "Mark all read", and the dot toggles
both ways. Only the API paths differ, because the list is plugin-owned (core's
unread count is one aggregate with no hook to carve one type out of it).

Every string is a translation key.

## Test plan

- [x] `for f in tests/*.test.js; do node "$f"; done` — all pass, including the
      updated topbar contract test
- [x] Live against a dev NodeBB as a `support:viewall` holder: badge count 4,
      four rows, per-entry read dot drops the badge to 3, Unread filter hides
      the read row, "Mark all read" clears every dot and hides the badge,
      empty state reads "Nothing new" — no console errors
- [x] Screenshotted side by side with the real notifications dropdown; the two
      are structurally identical

Depends on sow-nodebb-plugin-support#15 for the endpoints.

Generated with Claude CodeReviewed-on: #45

Co-authored-by: vickydotbat <vickydotbat@tutamail.com>

tests/global-topbar-contract.test.js

@@ -180,3 +180,17 @@ assertIncludes(
 	'.unread-dropdown',
 	'Topbar styles should cover the unread dropdown'
 );
+
+// Support case notifications live in the notification bell, added by
+// nodebb-plugin-support on core's own hooks. This theme owns nothing about
+// them, which is the point — see that plugin's ADR-0002.
+assert(
+	!/support/i.test(topbar),
+	'Topbar should carry no support-specific markup'
+);
+
+assertIncludes(
+	stylesheet,
+	'.wg-topbar .notifications-dropdown',
+	'Topbar styles should cover the notification dropdown'
+);