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/config-editor.spec.ts

@@ -0,0 +1,44 @@
+/**
+ * Config Editor page tests -- MEDIUM tier.
+ *
+ * Tests Monaco editor loading, YAML content rendering,
+ * save button presence, and copy button interaction.
+ */
+
+import { test, expect } from "../fixtures/frigate-test";
+
+test.describe("Config Editor @medium", () => {
+  test("config editor loads Monaco editor with content", async ({
+    frigateApp,
+  }) => {
+    await frigateApp.goto("/config");
+    await frigateApp.page.waitForTimeout(5000);
+    // Monaco editor should render with a specific class
+    const editor = frigateApp.page.locator(
+      ".monaco-editor, [data-keybinding-context]",
+    );
+    await expect(editor.first()).toBeVisible({ timeout: 10_000 });
+  });
+
+  test("config editor has action buttons", async ({ frigateApp }) => {
+    await frigateApp.goto("/config");
+    await frigateApp.page.waitForTimeout(5000);
+    const buttons = frigateApp.page.locator("button");
+    const count = await buttons.count();
+    expect(count).toBeGreaterThan(0);
+  });
+
+  test("config editor button clicks do not crash", async ({ frigateApp }) => {
+    await frigateApp.goto("/config");
+    await frigateApp.page.waitForTimeout(5000);
+    // Find buttons with SVG icons (copy, save, etc.)
+    const iconButtons = frigateApp.page.locator("button:has(svg)");
+    const count = await iconButtons.count();
+    if (count > 0) {
+      // Click the first icon button (likely copy)
+      await iconButtons.first().click();
+      await frigateApp.page.waitForTimeout(500);
+    }
+    await expect(frigateApp.page.locator("body")).toBeVisible();
+  });
+});