test(e2e): update suite for shipped features + gate Chromium-only perms

The running test container had been built from an older tree; rebuilding it to
pick up current app code surfaced several tests that predated shipped
security/UX features:

- file-upload-attacks / rate-limit: assert the magic-byte rejection wording and
  upload a real decodable JPEG (a zero-buffer is now rejected at the boundary).
- ddos: open SSE via the single-use /stream/ticket flow, not the dead ?token=.
- recover-page / join: the PIN field auto-submits on the 4th digit, so don't
  race an explicit submit click against the ensuing navigation.
- gestures-doubletap / sheet-escape: target the lightbox by aria-labelledby and
  anchor the radio accessible-name match at the start (gated dialog semantics).

playwright.config: camera/mic/clipboard are Chromium-only permissions (they threw
"Unknown permission: camera" on firefox/webkit and failed the test at context
creation); grant them per-Chromium-project. firefox-android drops the
unsupported isMobile flag.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

e2e/specs/02-upload/rate-limit.spec.ts

@@ -6,8 +6,12 @@
  */
 import { test, expect } from '../../fixtures/test';
 import { join } from 'node:path';
+import { readFileSync } from 'node:fs';
 
 const SAMPLE_JPG = join(process.cwd(), 'fixtures', 'media', 'sample.jpg');
+// A real, decodable JPEG — the upload handler validates magic bytes, so a
+// zero-filled buffer would be rejected with 400 before the rate limiter is reached.
+const SAMPLE_BYTES = readFileSync(SAMPLE_JPG);
 
 test.describe('Upload — rate limit', () => {
   test('4th upload in one hour returns 429 with Retry-After', async ({ api, adminToken, guest }) => {
@@ -24,7 +28,7 @@ test.describe('Upload — rate limit', () => {
     // Hit the API directly for speed — UI behavior is asserted in gallery-path.spec.
     const upload = async (n: number) => {
       const form = new FormData();
-      const blob = new Blob([new Uint8Array(640)], { type: 'image/jpeg' });
+      const blob = new Blob([SAMPLE_BYTES], { type: 'image/jpeg' });
       form.append('file', blob, `file${n}.jpg`);
       form.append('content_type', 'image/jpeg');
       return fetch((process.env.E2E_FRONTEND_URL ?? 'http://localhost:3101') + '/api/v1/upload', {
@@ -47,7 +51,6 @@ test.describe('Upload — rate limit', () => {
     // The 429 response carries Retry-After.
     const limited = responses.find((r) => r.status === 429)!;
     expect(limited.headers.get('retry-after')).toBeTruthy();
-    void SAMPLE_JPG;
   });
 
   test('flipping upload_rate_enabled off bypasses the limit', async ({ api, adminToken, guest }) => {
@@ -56,7 +59,7 @@ test.describe('Upload — rate limit', () => {
     const h = await guest('NoQuota');
     const upload = async (n: number) => {
       const form = new FormData();
-      const blob = new Blob([new Uint8Array(640)], { type: 'image/jpeg' });
+      const blob = new Blob([SAMPLE_BYTES], { type: 'image/jpeg' });
       form.append('file', blob, `file${n}.jpg`);
       form.append('content_type', 'image/jpeg');
       return fetch((process.env.E2E_FRONTEND_URL ?? 'http://localhost:3101') + '/api/v1/upload', {