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/specs/chat.spec.ts

@@ -0,0 +1,34 @@
+/**
+ * Chat page tests -- MEDIUM tier.
+ *
+ * Tests chat interface rendering, input area, and example prompt buttons.
+ */
+
+import { test, expect } from "../fixtures/frigate-test";
+
+test.describe("Chat Page @medium", () => {
+  test("chat page renders without crash", async ({ frigateApp }) => {
+    await frigateApp.goto("/chat");
+    await frigateApp.page.waitForTimeout(2000);
+    await expect(frigateApp.page.locator("body")).toBeVisible();
+  });
+
+  test("chat page has interactive input or buttons", async ({ frigateApp }) => {
+    await frigateApp.goto("/chat");
+    await frigateApp.page.waitForTimeout(2000);
+    const interactive = frigateApp.page.locator("input, textarea, button");
+    const count = await interactive.count();
+    expect(count).toBeGreaterThan(0);
+  });
+
+  test("chat input accepts text", async ({ frigateApp }) => {
+    await frigateApp.goto("/chat");
+    await frigateApp.page.waitForTimeout(2000);
+    const input = frigateApp.page.locator("input, textarea").first();
+    if (await input.isVisible().catch(() => false)) {
+      await input.fill("What cameras detected a person today?");
+      const value = await input.inputValue();
+      expect(value.length).toBeGreaterThan(0);
+    }
+  });
+});