feat: admin-provisioned staff, username login & role-based access

Replace the email-invitation flow with admin-provisioned staff accounts and
add role-based access that changes what each member sees.

Backend:
- Enable Better Auth `username` plugin (staff sign in by username); regenerate
  auth schema (+ username/displayUsername on user) and migration 0007.
- Add `doctor` and `reception` roles to the access-control RBAC. `reception` is
  scoped to scheduling + registration (no `prescription` statement).
- New `/api/staff` route: POST creates a user (auth.api.signUpEmail) and adds
  them to the active clinic (auth.api.addMember); GET lists members + usernames.
  Gated by requirePermission({ member: ["create"] }).
- Redact clinical PHI for the reception role in the patients service (read,
  create and update) so demographics-only is enforced server-side.

Frontend:
- usernameClient + Email|Username tabs on the login form.
- lib/roles.ts: useActiveRole + Better-Auth-permission-driven nav visibility,
  default landing, and a route guard (reception -> /appointments, blocked from
  clinical routes). Applied to the sidebar, command palette and auth guard.
- Care team page now provisions staff via a two-step Add-team-member dialog
  (details -> username/password) hitting /api/staff; removes the email-invite
  and pending-invitation UI. New members are contactable from Messages
  automatically (they become org members).
- Hide clinical sections of the patient form and the admin-only settings tabs
  for non-clinical/non-admin roles.

All permission management stays in Better Auth (per the better-auth skills now
referenced in backend/CLAUDE.md).

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

backend/src/index.ts

@@ -16,6 +16,7 @@ import { notesRouter } from "./routes/notes.js";
 import { notificationsRouter } from "./routes/notifications.js";
 import { patientsRouter } from "./routes/patients.js";
 import { prescriptionsRouter } from "./routes/prescriptions.js";
+import { staffRouter } from "./routes/staff.js";
 import { tasksRouter } from "./routes/tasks.js";
 
 const app = express();
@@ -58,6 +59,7 @@ app.use("/api/notes", notesRouter);
 app.use("/api/appointments", appointmentsRouter);
 app.use("/api/prescriptions", prescriptionsRouter);
 app.use("/api/tasks", tasksRouter);
+app.use("/api/staff", staffRouter);
 app.use("/api/activity", activityRouter);
 app.use("/api/analytics", analyticsRouter);
 app.use("/api/conversations", conversationsRouter);
@@ -78,6 +80,7 @@ server.listen(env.PORT, () => {
   console.log(`  • appts:    /api/appointments`);
   console.log(`  • rx:       /api/prescriptions`);
   console.log(`  • tasks:    /api/tasks`);
+  console.log(`  • staff:    /api/staff`);
   console.log(`  • activity: /api/activity`);
   console.log(`  • stats:    /api/analytics`);
   console.log(`  • messages: /api/conversations  (+ Socket.io)`);