[US-13.3 / OBT-244] Platform Overview: count pending change requests in the "Pending Requests" stat

Summary

The dashboard's Platform Overview "Pending Requests" stat counted only pending access requests. Change requests — create_project, create_language, edit_language (Area 13) — also await admin review but were invisible in the count. This makes the stat sum pending access requests + pending change requests, matching the card's own "Aggregate counts across the entire platform" framing. Both request fetches degrade gracefully, so a failure in one still renders the dashboard with what loaded.

Changes

1. Count both request types — src/components/pages/dashboard/AdminDashboard.tsx

• Fetch pending change requests alongside the existing calls via changeRequestsAPI.list({ status: "pending" }) (no new endpoint).
• AdminData gains pendingChangeRequests: ChangeRequestResponse[].
• The "Pending Requests" StatCard value and highlight now use totalPending = pendingRequests.length + pendingChangeRequests.length.
• Both the access-requests and change-requests fetches get a .catch(() => ({ data: [] })), so one failing endpoint no longer drops the whole dashboard — the overview renders and counts what it could load (stats are non-critical).

The existing "Pending Access Requests" detail panel is unchanged: it still lists access requests only (reviewed on the Users page); change requests are reviewed on the Projects/Languages pages.

Type of Change

• Feature (Platform Overview now reflects pending change requests)

Testing

• npm run typecheck (tsc -b) — pass
• npm run lint (eslint .) — 0 errors
• npm run build (vite build) — pass
• Manual (on the local integration branch, logged in as platform admin): with N pending access requests and M pending change requests seeded, the "Pending Requests" card shows N + M and highlights when > 0; rejecting/approving a change request lowers the count on next dashboard load.

Stacked on US-13.2 / OBT-243 (PR #31). This branch depends on changeRequestsAPI / ChangeRequestResponse, which are introduced by #31 and are not yet on main. PR base is the obt-243 branch so the diff shows only this change. Merge order: #31 first, then this; rebase onto main once #31 lands.