feat(workspace): claudemesh me notifications + dashboard parity

ships v0.4.0 phase 3.

api: GET /v1/me/notifications aggregates the mesh.notification
table across every joined mesh in a 7-day window (?since=iso
overrides, ?include=all surfaces already-read). returns sender +
topic + mesh context plus a 240-char snippet for v1 plaintext
messages or raw ciphertext for v2 (the dashboard topic-key cache
decrypts client-side).

cli (1.12.0): claudemesh me notifications — terse unread feed
with @ dot, --all to include read, --since for custom window.

web: /dashboard/notifications mirrors the cli view in card form,
adds a notifications entry to the dashboard sidebar between
topics and invites. each card links straight to the topic chat.

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

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

@@ -30,6 +30,11 @@ const menu = [
         href: pathsConfig.dashboard.user.topics,
         icon: Icons.MessageSquare,
       },
+      {
+        title: "notifications",
+        href: pathsConfig.dashboard.user.notifications,
+        icon: Icons.Bell,
+      },
       {
         title: "invites",
         href: pathsConfig.dashboard.user.invites,