Merge feature/gro-118-better-auth into fix/gro-153-dev-login-staff-resolution

Resolve merge conflict in rbac.ts: keep PR branch logic
(try userId first, then fall back to staff.id) rather than
base branch's staff.id-only approach.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/__tests__/rbac.test.ts

@@ -168,7 +168,7 @@ describe("resolveStaffMiddleware", () => {
     });
 
     const res = await app.request("/test", {
-      headers: { "X-Dev-User-Id": GROOMER.userId! },
+      headers: { "X-Dev-User-Id": GROOMER.id },
     });
     expect(res.status).toBe(200);
     expect(capturedStaff!.role).toBe("groomer");