frontend: messages search, care-team employee dialog, PCP picker + transfer, activity detail, analytics grid

- Messages: search the inbox and the compose member picker.
- Care Team: clickable member rows open an employee dialog showing role +
  permissions, with change-role (updateMemberRole) and remove.
- Patients: Primary Care is now a provider dropdown (defaults to self for a
  doctor); add a Transfer action + dialog wired to the transfer API.
- Activity: entries are clickable, opening a detail dialog.
- Analytics: Section takes a columns prop so each row fills evenly (no orphan
  card in Appointments).
- Add lib/staff.ts (listProviders), transferPatient client, rolePermissionSummary
  helper, and i18n keys for all new strings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/lib/staff.ts

@@ -0,0 +1,14 @@
+import { apiFetch } from "@/lib/api-client";
+
+// A clinician who can be assigned as a patient's primary provider. Returned by
+// the backend's GET /api/staff/providers (clinical roles only — excludes
+// reception/viewer). Readable by any clinic member.
+export type Provider = {
+  userId: string;
+  name: string;
+  role: string;
+};
+
+export function listProviders(): Promise<Provider[]> {
+  return apiFetch<Provider[]>("/api/staff/providers");
+}