fix(e2e): switch mobile project to chromium and repair spec flakiness

Three orthogonal fixes that account for most of the e2e suite's
ongoing red:

- The `chromium-mobile` project was actually iPhone 13 (webkit) — CI's
  `playwright install chromium` therefore could not launch it
  (`webkit-2272/pw_run.sh` does not exist). Renaming-to-Pixel-5 makes
  the project name match what the runner provides without expanding
  the install footprint.
- `locale-switch.spec.ts` tried to anchor the cookie at `page.url()`,
  which on a fresh context is `about:blank`; Playwright rejected the
  cookie outright. Using the project's configured baseURL is the
  documented way and works regardless of navigation timing.
- `login.spec.ts` looked for the username/password inputs immediately
  after navigation, but the password form is mounted lazily once the
  user clicks "Login with password" (passkey is the default mode).
  A small helper now opens the form before the assertions run.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

e2e/locale-switch.spec.ts

@@ -16,11 +16,16 @@ test.describe("locale switch", () => {
       page,
       context,
     }) => {
+      // Cookies must be addressable to a real origin — `page.url()` on
+      // a fresh context returns `about:blank`, which Playwright rejects.
+      // Anchor at the configured base URL explicitly.
+      const baseURL =
+        test.info().project.use.baseURL ?? "http://localhost:3000";
       await context.addCookies([
         {
           name: "healthlog_locale",
           value: locale,
-          url: page.url() || "http://localhost:3000",
+          url: baseURL,
         },
       ]);
       await page.goto("/auth/login");

e2e/login.spec.ts

@@ -9,13 +9,25 @@ import { expect, test } from "@playwright/test";
  * roundtrip is exercised by the integration test in
  * tests/integration/auth-flow.test.ts.
  */
+async function openPasswordForm(page: import("@playwright/test").Page) {
+  await page.goto("/auth/login");
+  // The login page defaults to passkey mode; the password form is
+  // mounted only after clicking the "Login with password" / "Mit
+  // Passwort anmelden" outline button.
+  await page
+    .getByRole("button", { name: /login with password|mit passwort/i })
+    .click();
+}
+
 test.describe("login page", () => {
   test("renders username + password inputs with the right autoComplete", async ({
     page,
   }) => {
-    await page.goto("/auth/login");
+    await openPasswordForm(page);
 
-    const username = page.getByLabel(/username|benutzername/i).first();
+    const username = page
+      .getByLabel(/username|benutzername|email|e-mail/i)
+      .first();
     await expect(username).toBeVisible();
     await expect(username).toHaveAttribute("autoComplete", /username|email/);
 
@@ -25,10 +37,10 @@ test.describe("login page", () => {
   });
 
   test("rejects an obviously-wrong credential pair", async ({ page }) => {
-    await page.goto("/auth/login");
+    await openPasswordForm(page);
 
     await page
-      .getByLabel(/username|benutzername/i)
+      .getByLabel(/username|benutzername|email|e-mail/i)
       .first()
       .fill("nobody-here");
     await page.locator('input[type="password"]').first().fill("not-the-pw");

playwright.config.ts

@@ -44,7 +44,11 @@ export default defineConfig({
     {
       name: "chromium-mobile",
       use: {
-        ...devices["iPhone 13"],
+        // Pixel 5 — Chromium-based mobile profile so CI only needs
+        // `playwright install chromium` instead of also pulling
+        // webkit. iPhone-13 is intentionally avoided here; the
+        // mobile-Safari smoke is exercised by the iOS app suite.
+        ...devices["Pixel 5"],
       },
     },
   ],