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/fixtures/api-client.ts

@@ -0,0 +1,152 @@
+/**
+ * Tiny typed wrapper around the EventSnap REST API for use inside tests.
+ * Used to seed data far faster than driving the UI through every join /
+ * upload, and to set up adversarial states (banned users, locked PINs) that
+ * the UI cannot reach.
+ *
+ * Auth: pass `token` on individual calls; no global state.
+ */
+
+export const ADMIN_PASSWORD = 'admin-test-pw';
+
+export class ApiClient {
+  constructor(private baseUrl: string = process.env.E2E_FRONTEND_URL ?? 'http://localhost:3101') {}
+
+  private async request<T>(
+    method: string,
+    path: string,
+    opts: { token?: string; body?: unknown; expectedStatus?: number | number[] } = {}
+  ): Promise<{ status: number; body: T }> {
+    const headers: Record<string, string> = {};
+    if (opts.token) headers['Authorization'] = `Bearer ${opts.token}`;
+    if (opts.body !== undefined) headers['Content-Type'] = 'application/json';
+
+    const res = await fetch(`${this.baseUrl}/api/v1${path}`, {
+      method,
+      headers,
+      body: opts.body !== undefined ? JSON.stringify(opts.body) : undefined,
+    });
+
+    const expected = opts.expectedStatus ?? [200, 201, 204];
+    const allowed = Array.isArray(expected) ? expected : [expected];
+    let body: unknown = undefined;
+    if (res.status !== 204) {
+      const text = await res.text();
+      try {
+        body = text.length > 0 ? JSON.parse(text) : undefined;
+      } catch {
+        body = text;
+      }
+    }
+    if (!allowed.includes(res.status)) {
+      throw new Error(
+        `API ${method} ${path} → ${res.status} (expected ${allowed.join('/')}). Body: ${JSON.stringify(body)}`
+      );
+    }
+    return { status: res.status, body: body as T };
+  }
+
+  // ── Auth ───────────────────────────────────────────────────────────────
+  async join(displayName: string): Promise<{ jwt: string; pin: string; user_id: string; is_new: boolean }> {
+    const { body } = await this.request<any>('POST', '/join', {
+      body: { display_name: displayName },
+      expectedStatus: [201],
+    });
+    return body;
+  }
+
+  async recover(displayName: string, pin: string, opts: { expectedStatus?: number | number[] } = {}) {
+    return this.request<any>('POST', '/recover', {
+      body: { display_name: displayName, pin },
+      expectedStatus: opts.expectedStatus ?? [200],
+    });
+  }
+
+  async adminLogin(password: string = ADMIN_PASSWORD): Promise<string> {
+    const { body } = await this.request<{ jwt: string }>('POST', '/admin/login', {
+      body: { password },
+    });
+    return body.jwt;
+  }
+
+  async logout(token: string) {
+    return this.request<void>('DELETE', '/session', { token, expectedStatus: [204] });
+  }
+
+  // ── Test-mode helpers ──────────────────────────────────────────────────
+  async truncate(adminToken: string) {
+    return this.request<void>('POST', '/admin/__truncate', {
+      token: adminToken,
+      expectedStatus: [204],
+    });
+  }
+
+  // ── Config ─────────────────────────────────────────────────────────────
+  async patchConfig(adminToken: string, patch: Record<string, string>) {
+    return this.request<void>('PATCH', '/admin/config', {
+      token: adminToken,
+      body: patch,
+      expectedStatus: [204],
+    });
+  }
+
+  async getConfig(adminToken: string): Promise<Record<string, string>> {
+    const { body } = await this.request<Record<string, string>>('GET', '/admin/config', { token: adminToken });
+    return body;
+  }
+
+  // ── Host moderation ────────────────────────────────────────────────────
+  async listUsers(token: string) {
+    const { body } = await this.request<any[]>('GET', '/host/users', { token });
+    return body;
+  }
+
+  async setRole(token: string, userId: string, role: 'guest' | 'host') {
+    return this.request<void>('PATCH', `/host/users/${userId}/role`, {
+      token,
+      body: { role },
+      expectedStatus: [200, 204],
+    });
+  }
+
+  async banUser(token: string, userId: string, hideUploads = false) {
+    return this.request<void>('POST', `/host/users/${userId}/ban`, {
+      token,
+      body: { hide_uploads: hideUploads },
+      expectedStatus: [200, 204],
+    });
+  }
+
+  async closeEvent(token: string) {
+    return this.request<void>('POST', '/host/event/close', { token, expectedStatus: [200, 204] });
+  }
+
+  async openEvent(token: string) {
+    return this.request<void>('POST', '/host/event/open', { token, expectedStatus: [200, 204] });
+  }
+
+  // ── Feed ───────────────────────────────────────────────────────────────
+  async getFeed(token: string) {
+    const { body } = await this.request<any>('GET', '/feed', { token });
+    return body;
+  }
+
+  async getStats(adminToken: string) {
+    const { body } = await this.request<any>('GET', '/admin/stats', { token: adminToken });
+    return body;
+  }
+
+  // ── Health ─────────────────────────────────────────────────────────────
+  async waitForHealth(retries = 60): Promise<void> {
+    for (let i = 0; i < retries; i++) {
+      try {
+        const res = await fetch(`${this.baseUrl}/health`);
+        if (res.ok) return;
+      } catch {
+        /* keep retrying */
+      }
+      await new Promise((r) => setTimeout(r, 1000));
+    }
+    throw new Error(`Backend never became healthy at ${this.baseUrl}/health`);
+  }
+}