Add frontend tests (#22783)

* basic e2e frontend test framework

* improve mock data generation and add test cases

* more cases

* add e2e tests to PR template

* don't generate mock data in PR CI

* satisfy codeql check

* fix flaky system page tab tests by guarding against crashes from incomplete mock stats

* reduce local test runs to 4 workers to match CI

web/e2e/fixtures/mock-data/profile.ts

@@ -0,0 +1,39 @@
+/**
+ * User profile factories for E2E tests.
+ */
+
+export interface UserProfile {
+  username: string;
+  role: string;
+  allowed_cameras: string[] | null;
+}
+
+export function adminProfile(overrides?: Partial<UserProfile>): UserProfile {
+  return {
+    username: "admin",
+    role: "admin",
+    allowed_cameras: null,
+    ...overrides,
+  };
+}
+
+export function viewerProfile(overrides?: Partial<UserProfile>): UserProfile {
+  return {
+    username: "viewer",
+    role: "viewer",
+    allowed_cameras: null,
+    ...overrides,
+  };
+}
+
+export function restrictedProfile(
+  cameras: string[],
+  overrides?: Partial<UserProfile>,
+): UserProfile {
+  return {
+    username: "restricted",
+    role: "viewer",
+    allowed_cameras: cameras,
+    ...overrides,
+  };
+}