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/config/paths.ts

@@ -103,6 +103,7 @@ const pathsConfig = {
         topic: (id: string, name: string) =>
           `${DASHBOARD_PREFIX}/meshes/${id}/topics/${encodeURIComponent(name)}`,
       },
+      topics: `${DASHBOARD_PREFIX}/topics`,
       invites: `${DASHBOARD_PREFIX}/invites`,
       settings: {
         index: `${DASHBOARD_PREFIX}/settings`,