feat(dashboard): merge Analytics into Dashboard, remove Kanban Board

Closes issue #5 (Dashboard | Update menu & page):
- Analytics content (heatmap, sparkline, token/cost/workflow/productivity
  charts) moves into a new "Analytics" tab on the Dashboard page, alongside
  the existing Monitor/Health tabs. The standalone Analytics page, its
  /analytics route, and its sidebar menu entry are removed.
- The Kanban Board page, its /kanban route, and its sidebar menu entry are
  removed entirely (page content deleted, not just hidden).
- Updated ARCHITECTURE.md, README.md, client/README.md, docs/API.md, and
  the affected client tests/snapshots to match.

docs/API.md

@@ -1496,7 +1496,7 @@ DELETE /api/run/:id                   Kill (SIGTERM → SIGKILL after 5 s)
 
 **PTY streaming:** Frames from the tmux pane are streamed to the client over `/ws-pty/:runId` as binary WebSocket frames (not JSON). The Workspace page's TerminalView component feeds these frames to xterm.js for live rendering. Simultaneously, `ccam lanes shell` can attach the same session via a real local terminal, staying in sync with the browser view.
 
-Every history row carries `lane_id`: the lane whose run it belongs to. `GET /api/run/history?laneId=<n>` returns only that lane's runs. Spawned `claude` processes fire the dashboard's hooks like any other CLI session, so they show up in `/api/sessions`, the analytics, the Kanban board, and the Workflows page automatically.
+Every history row carries `lane_id`: the lane whose run it belongs to. `GET /api/run/history?laneId=<n>` returns only that lane's runs. Spawned `claude` processes fire the dashboard's hooks like any other CLI session, so they show up in `/api/sessions`, the Dashboard's Analytics tab, and the Workflows page automatically.
 
 ---