feat(e2e): Playwright suite — 134 tests across 9 spec areas + UA matrix

Adds an end-to-end Playwright test suite under e2e/ that spins up an
isolated docker-compose stack (Postgres :55432, Caddy :3101, backend with
EVENTSNAP_TEST_MODE=1, SvelteKit adapter-node frontend) and exercises the
SvelteKit app against the real Rust backend.

Phase 1 — happy paths covering every documented USER_JOURNEYS.md flow:
  01-auth/      join, recover, admin login, leave event, PIN lockout
  02-upload/    gallery picker (API path), rate-limit + admin toggle
  03-feed/      like/comment SSE, filters, SSE reconnect on visibility
  04-host/      event lock API, ban/unban, promote
  05-admin/     config validation, foundational authz guards, stats
  06-export/    /export status + download stub
  __smoke/      cross-UA happy-path (runs on every UA project)

Phase 2 — adversarial + browser chaos:
  07-adversarial/  XSS payloads (6 × display name path), SQLi shapes,
                   length / encoding / RTL override / NUL byte;
                   file-upload boundaries (ELF body claimed as JPEG,
                   oversize vs max_image_size_mb, zero-byte, NUL
                   filename, path-traversal, SVG-with-script);
                   JWT alg:none, signature/payload tamper, expired
                   session, PIN brute-force (serial + parallel),
                   admin password brute-force; deep authz (cross-user
                   delete, banned user across like/comment/feed-read,
                   host→admin escalation); small-scale DDoS (20× /join,
                   10MB comment body, 10 concurrent SSE).
  08-browser-chaos/ localStorage / sessionStorage / cookie purge,
                    IndexedDB drop mid-session, offline → reconnect,
                    slow-3G, 503 flakes, 429 with no retry storm,
                    multi-tab same/different user, no-JS, hostile CSS,
                    clock skew ±1h / -2d, localStorage quota exhausted.

Phase 3 — mobile gestures (runs only on chromium-mobile / Pixel 7):
  09-mobile/    touch-target ≥44px audit, env(safe-area-inset-bottom)
                structural check, long-press (FeedListCard → ContextSheet,
                quick-tap negation, click-suppression), double-tap
                (feed card like + lightbox heart-burst, via synthetic
                pointer events to bypass the first-tap-fires-click trap),
                viewport reflow (portrait/landscape/narrow/phablet),
                plus fixme stubs documenting planned gestures (swipe
                lightbox L/R, swipe-down dismiss, pull-to-refresh,
                long-press-comment).

Cross-UA matrix (chromium-engine projects run @smoke only):
  chromium-pixel7, chromium-galaxy-s22, samsung-internet (Samsung UA
  emulation on Galaxy viewport), edge-android, plus webkit-iphone,
  chrome-ios, firefox-android, firefox-desktop — the latter four need
  libavif16 on the host (Playwright dep) but the configs are in place.

Infrastructure:
  - fixtures/test.ts central test.extend (api, db, adminToken, guest,
    host, signIn). Per-test DB truncate via the dev-only POST
    /admin/__truncate route, gated by EVENTSNAP_TEST_MODE=1.
  - helpers/sse-listener.ts, helpers/upload-client.ts (Node-side
    multipart for adversarial file-upload tests + JPEG/PNG/ELF magic
    constants), helpers/touch.ts (longPress / doubleTap / swipe /
    inlineStyle / computedStyle).
  - 10 page objects covering every route + UploadSheet/Lightbox.
  - global-setup waits for /health, logs in admin, disables every
    rate-limit and quota toggle.
  - .github/workflows/e2e.yml: PR check runs chromium-desktop + the
    smoke matrix in parallel, uploads playwright-report/ and traces on
    failure.

Findings the suite surfaces as live `[finding]` warnings (not silenced):
  1. /admin/login has no rate-limit or lockout (bcrypt cost only).
  2. PIN-attempt counter races under parallel /recover requests.
  3. Zero-byte uploads pass /api/v1/upload.
  4. SVG-with-script can pass the magic-byte check (consider CSP +
     X-Content-Type-Options on /media/*).

Stack-internal docs live in e2e/README.md (UA tier table, Samsung
Internet escalation tiers A/B/C, debugging tips, roadmap).

Final tally: 134 passed / 0 failed / 9 skipped (test.fixme stubs for
not-yet-shipped gestures and one UI-upload-flow investigation).

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

e2e/specs/07-adversarial/ddos.spec.ts

@@ -0,0 +1,77 @@
+/**
+ * Phase 2 adversarial — small-scale DDoS / oversized-body tests. These are
+ * NOT real load tests. We just verify that obvious abuse is rate-limited
+ * or rejected gracefully without crashing the backend.
+ */
+import { test, expect } from '../../fixtures/test';
+
+const BASE = process.env.E2E_FRONTEND_URL ?? 'http://localhost:3101';
+
+test.describe('Adversarial — small-scale abuse', () => {
+  // Note: the truncate auto-fixture resets every rate-limit toggle back to false
+  // before each test, so we re-enable in beforeEach (not beforeAll).
+  test.beforeEach(async ({ api, adminToken }) => {
+    await api.patchConfig(adminToken, { rate_limits_enabled: 'true', join_rate_enabled: 'true' });
+  });
+
+  test('20 parallel /join from one IP — rate limiter catches the excess', async () => {
+    const requests = Array.from({ length: 20 }, (_, i) =>
+      fetch(`${BASE}/api/v1/join`, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ display_name: `Flood${i}_${Date.now()}` }),
+      })
+    );
+    const statuses = (await Promise.all(requests)).map((r) => r.status);
+    // 5/min limit → at least some should be 429.
+    expect(statuses.filter((s) => s === 429).length).toBeGreaterThan(0);
+    // Server stays up — at least one succeeded.
+    expect(statuses.some((s) => s === 201 || s === 409)).toBe(true);
+  });
+
+  test('10 MB comment body is rejected (multipart-less endpoint)', async ({ guest }) => {
+    const g = await guest('BigComment');
+    const huge = 'A'.repeat(10 * 1024 * 1024);
+    const res = await fetch(`${BASE}/api/v1/upload/00000000-0000-0000-0000-000000000000/comments`, {
+      method: 'POST',
+      headers: { Authorization: `Bearer ${g.jwt}`, 'Content-Type': 'application/json' },
+      body: JSON.stringify({ body: huge }),
+    });
+    // 400 (length cap), 404 (no such upload), 413 (payload too large), 429 (rate-limited),
+    // or 502 (Caddy rejected the body before it reached the backend) — all fine.
+    expect([400, 404, 413, 429, 502]).toContain(res.status);
+    // Not 200 — that would mean we accepted a 10 MB comment.
+    expect(res.status).not.toBe(200);
+  });
+
+  test('SSE: 10 concurrent streams from one user do not crash the server', async ({ guest }) => {
+    const g = await guest('SseFlood');
+    const controllers = Array.from({ length: 10 }, () => new AbortController());
+    const requests = controllers.map((c) =>
+      fetch(`${BASE}/api/v1/stream?token=${encodeURIComponent(g.jwt)}`, { signal: c.signal })
+    );
+    const responses = await Promise.all(requests);
+    // All accepted (or some rate-limited — both fine).
+    for (const r of responses) {
+      expect([200, 429]).toContain(r.status);
+    }
+    // Tear them all down so the next test doesn't see leaked connections.
+    controllers.forEach((c) => c.abort());
+
+    // Sanity: a new request still works.
+    const ping = await fetch(`${BASE}/api/v1/me/context`, {
+      headers: { Authorization: `Bearer ${g.jwt}` },
+    });
+    expect(ping.status).toBe(200);
+  });
+
+  test('malformed JSON in /join is rejected with 400, not 500', async () => {
+    const res = await fetch(`${BASE}/api/v1/join`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: '{"display_name":',
+    });
+    expect([400, 422]).toContain(res.status);
+    expect(res.status).not.toBe(500);
+  });
+});