fix(review-2): critical — repair comment posting + close export data leak

CR1: the lightbox comment button POSTed to /upload/{id}/comment (singular);
     no such route exists, so every UI-submitted comment 404'd and was lost.
     Fixed to /comments (plural). The prior e2e passed because its seed helper
     POSTs the API directly — added comment-ui.spec.ts which drives the real
     component so this can't regress silently again.

CR2: export archives (Gallery.zip / Memories.zip / HTML viewer) were written
     under media_path, which is a public ServeDir — so GET /media/exports/
     Gallery.zip served the entire event (every photo, caption, comment,
     uploader name) to any anonymous visitor at a guessable URL, bypassing the
     ticket + release gate. Moved exports to a separate EXPORT_PATH (=/exports)
     on its own volume (Dockerfile chown, compose volume, gated handler reads
     the new path). export-leak.spec.ts asserts /media/exports/Gallery.zip → 404.

Riders (git can't split hunks): LightboxModal also gains H3 live-eviction on
comment-deleted/upload-deleted; config.rs also wires compression_concurrency
from boot config (medium).

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

e2e/specs/03-feed/comment-ui.spec.ts

@@ -0,0 +1,53 @@
+/**
+ * Regression for the review's CR1: the LightboxModal posted comments to
+ * `/upload/{id}/comment` (singular) while the only route is `/comments` (plural),
+ * so every comment submitted through the UI 404'd and was silently lost. The
+ * earlier "comment → SSE" spec passed by posting via a fetch helper, bypassing
+ * the component — a false green. This drives the real component end-to-end.
+ */
+import { test, expect } from '../../fixtures/test';
+import { seedUpload } from '../../helpers/seed';
+
+const BASE = process.env.E2E_FRONTEND_URL ?? 'http://localhost:3101';
+
+test.describe('Comments — UI round-trip (CR1)', () => {
+  test('a comment typed in the lightbox persists to the backend', async ({
+    page,
+    guest,
+    signIn,
+  }) => {
+    const author = await guest('CommentAuthor');
+    const commenter = await guest('Commenter');
+    const uploadId = await seedUpload(author.jwt, { caption: 'Comment target' });
+
+    await signIn(page, commenter);
+    await page.goto('/feed');
+
+    // Open the lightbox. Only one upload exists, so the first open-button is it.
+    const imageButton = page.getByRole('button', { name: 'Bild vergrößern' }).first();
+    await expect(imageButton).toBeVisible({ timeout: 15_000 });
+    await imageButton.click();
+
+    const lightbox = page.locator('[role="dialog"][aria-labelledby="lightbox-title"]');
+    await expect(lightbox).toBeVisible();
+
+    const text = `Wunderschönes Foto ${Date.now()}`;
+    await lightbox.getByPlaceholder(/kommentar/i).fill(text);
+    await lightbox.getByRole('button', { name: /senden/i }).click();
+
+    // The component appends the comment only on a 2xx — with the old singular path
+    // it threw and nothing appeared. Assert it's visible in the panel...
+    await expect(lightbox.getByText(text)).toBeVisible();
+
+    // ...and that it actually persisted server-side (the crux CR1 broke).
+    await expect
+      .poll(async () => {
+        const res = await fetch(`${BASE}/api/v1/upload/${uploadId}/comments`, {
+          headers: { Authorization: `Bearer ${commenter.jwt}` },
+        });
+        const body = await res.json();
+        return Array.isArray(body) && body.some((c: { body: string }) => c.body === text);
+      })
+      .toBe(true);
+  });
+});

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

@@ -0,0 +1,22 @@
+/**
+ * Regression for the review's CR2: export archives (Gallery.zip / Memories.zip)
+ * were written under media_path/exports, and /media is a public ServeDir — so
+ * anyone could GET /media/exports/Gallery.zip and download the whole gallery,
+ * bypassing the ticket + export_*_ready gate. Exports now live OUTSIDE media_path
+ * and are reachable only via the gated /api/v1/export/{zip,html} handlers (covered
+ * by export.spec.ts). Here we assert the public path is dead.
+ */
+import { test, expect } from '../../fixtures/test';
+
+const BASE = process.env.E2E_FRONTEND_URL ?? 'http://localhost:3101';
+
+test.describe('Export — no public leak (CR2)', () => {
+  test('archives are not reachable through the public /media path', async () => {
+    for (const name of ['Gallery.zip', 'Memories.zip']) {
+      const res = await fetch(`${BASE}/media/exports/${name}`);
+      // 404 (not 200): a 200 here would mean the whole-gallery archive is
+      // downloadable without any auth — the CR2 data-exposure regression.
+      expect(res.status).toBe(404);
+    }
+  });
+});