feat(workspace): claudemesh me topics + dashboard topics page

ships v0.4.0 phase 2: a cross-mesh topic feed.

api: GET /v1/me/topics aggregates topics across every mesh the
caller belongs to with per-topic unread counts (vs the user's
member-row last_read_at) and last-message timestamps. Sorted by
last activity.

cli (1.11.0): claudemesh me topics renders the feed; --unread
filters to topics with pending reads; --json returns raw.

web: /dashboard/topics ssr's the same view server-side (direct
db queries, no apikey-mint roundtrip) and adds a Topics entry
to the dashboard sidebar between Meshes and Invites.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/app/[locale]/dashboard/(user)/layout.tsx

@@ -25,6 +25,11 @@ const menu = [
         href: pathsConfig.dashboard.user.meshes.index,
         icon: Icons.Share,
       },
+      {
+        title: "topics",
+        href: pathsConfig.dashboard.user.topics,
+        icon: Icons.MessageSquare,
+      },
       {
         title: "invites",
         href: pathsConfig.dashboard.user.invites,