feat(workspace): claudemesh me activity + dashboard parity

ships v0.4.0 phase 4. final aggregating verb after this is
me search (phase 5).

api: GET /v1/me/activity returns topic messages across every
mesh the user belongs to in a 24h default window (?since=iso
override), excluding messages the caller authored themselves.
"what is happening that i missed", capped at 200.

cli (1.13.0): claudemesh me activity prints a condensed feed
with mesh + topic + sender + relative timestamp + snippet (or
[encrypted] for v2 ciphertext).

web: /dashboard/activity clusters consecutive messages from the
same topic into thread blocks for readability. sidebar gains an
activity entry between notifications and invites.

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

apps/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "claudemesh-cli",
-  "version": "1.12.0",
+  "version": "1.13.0",
   "description": "Peer mesh for Claude Code sessions — CLI + MCP server.",
   "keywords": [
     "claude-code",