test(e2e): pin security assertions + real cross-user IDOR coverage

Turn "accept-both-outcomes" documentation tests — which pass whether the app is
secure or vulnerable — into assertions that pin the secure behavior, and replace
fake-UUID authz tests that 404'd before ever reaching the ownership guard with
real cross-user resources.

file-upload-attacks:
- SVG-with-<script> → pin 400 (infer returns None for text → stored-XSS defense);
  was [201,400], which accepted the vulnerable outcome.
- zero-byte → pin 400; path-traversal → pin 201 with UUID-derived storage and a
  no-path-echo check (both were [201,400]).
- Fix the application/octet-stream rationale (no "application bypass" exists — the
  handler ignores the declared type and keys off magic bytes).

authorization-deep (IDOR):
- B deleting A's comment: seed a real upload+comment as A, assert 403, assert the
  comment survives, and assert the owner (A) still gets 204 — proving the 403 is
  about identity, not a broken route. (Was a DELETE on the all-zeros UUID → 404
  before the user_id guard, so authorization was never exercised.)
- Add B-deletes-A's-upload (403, countUploads unchanged) and B-edits-A's-caption
  (403, caption intact) — the find_by_id_and_event + ownership guards.

export: pin the ZIP-download 404 (was [404,200] — a 200 is a data-exposure
regression) and split into the two real branches: not-yet-ready, and
ready-but-file-missing (new db.setExportZipReady helper).

All 21 assertions verified green against the live secure backend.

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

e2e/specs/06-export/export.spec.ts

@@ -42,22 +42,42 @@ test.describe('Export — release and download', () => {
     expect(body.html.status).toBe('done');
   });
 
-  test('ZIP download returns 404 when no file is on disk (export released but never compressed)', async ({ guest, db }) => {
-    const g = await guest('NoFile');
+  const base = process.env.E2E_FRONTEND_URL ?? 'http://localhost:3101';
+
+  // Browser downloads stream to disk via a top-level navigation, so the download
+  // endpoint authenticates with a single-use ticket (no Bearer header).
+  async function mintTicket(jwt: string): Promise<string> {
+    const res = await fetch(base + '/api/v1/export/ticket', {
+      method: 'POST',
+      headers: { Authorization: `Bearer ${jwt}` },
+    });
+    return (await res.json()).ticket;
+  }
+
+  test('ZIP download 404s when the export is not yet marked ready', async ({ guest, db }) => {
+    const g = await guest('NotReady');
+    // Released flag set, but export_zip_ready is still false → must refuse, never serve.
     await db.setExportReleased(SLUG, true);
     await db.fakeExportJob(SLUG, 'zip', 'done');
-    const base = process.env.E2E_FRONTEND_URL ?? 'http://localhost:3101';
-    // Browser downloads stream straight to disk via a top-level navigation, so the
-    // download endpoint authenticates with a single-use ticket (no Bearer header).
-    const ticketRes = await fetch(base + '/api/v1/export/ticket', {
-      method: 'POST',
-      headers: { Authorization: `Bearer ${g.jwt}` },
-    });
-    const { ticket } = await ticketRes.json();
-    // Real backend additionally checks event.export_zip_ready. The faked row is
-    // enough for /status; the download path needs the boolean flag too.
+    const ticket = await mintTicket(g.jwt);
+
     const res = await fetch(base + '/api/v1/export/zip?ticket=' + encodeURIComponent(ticket));
-    // Either 404 ("not available" OR "file not found") — both are valid states for this setup.
-    expect([404, 200]).toContain(res.status);
+    // Pinned to 404 (not [404,200]): a 200 here would mean serving an export that was
+    // never released for download — a data-exposure regression. This hits the
+    // `!export_zip_ready` guard.
+    expect(res.status).toBe(404);
+  });
+
+  test('ZIP download 404s when marked ready but the file is missing on disk', async ({ guest, db }) => {
+    const g = await guest('ReadyNoFile');
+    // Released AND ready, but no Gallery.zip on disk (we never ran a real export) →
+    // the handler must 404 on the missing-file check, not 200/500 or serve a stale file.
+    await db.setExportReleased(SLUG, true);
+    await db.setExportZipReady(SLUG, true);
+    await db.fakeExportJob(SLUG, 'zip', 'done');
+    const ticket = await mintTicket(g.jwt);
+
+    const res = await fetch(base + '/api/v1/export/zip?ticket=' + encodeURIComponent(ticket));
+    expect(res.status).toBe(404);
   });
 });