fix: security, performance and correctness pass; add sidecar archive support

Security
- Fix path traversal in GET /api/archives/:name/files. Express decodes route
  params after segment matching, so `..%2f..%2fetc` escaped ARCHIVES_DIR and
  returned a recursive listing of arbitrary directories.
- Add CSP and baseline security headers; disable x-powered-by.
- Stop baking GEMINI_API_KEY into the client bundle (the SDK was unused).
- Run the container as `node` instead of root.

Performance
- Add a directory-mtime-keyed archive index, warmed in the background and
  persisted. Listing 110k files went from ~52s to ~0.1s; the largest archive
  (24k files) serves in ~0.3s. Per-file stat over CIFS costs ~1.4ms and does
  not parallelise, so it is now done once rather than per request.
- Build media URLs from the File directly instead of
  `new Blob([await file.arrayBuffer()])`, which read every media file fully
  into memory (a 20GB archive tried to become 20GB of resident blobs).
- Track and revoke object URLs; previously none were ever revoked.
- Give `requestThumbnail` a stable identity so a completed thumbnail stops
  re-running the effect in every mounted thumbnail.
- Namespace IndexedDB keys so listing archives no longer deserializes every
  cached thumbnail blob, and thumbnails no longer collide across archives.
- Serve real file sizes: RemoteArchiveFile was constructed with size 0, which
  silently disabled high-res thumbnailing for every server archive.

Correctness
- Local archives cached media as blob: URLs, which die with the document, so
  a cached local archive restored as an archive of broken images. Media now
  carries a stable path and is rehydrated from a persisted directory handle
  (File System Access API), falling back to re-prompting for the folder.
- Fix permalinks: the URL-writing effect erased ?a= on mount before the
  archive list arrived to consume it, so deep links never resolved.
- Make cache invalidation detect nested changes via a directory signature.
- Add an error boundary and tolerate unparseable dates, which previously
  threw a RangeError and blanked the app.
- Default video to muted so autoplay is not blocked by Safari/Firefox.

Features
- Fold sidecar directories into their base profile: `<user> - reels`,
  `story - <user>` and `story highlights - <user> - <title>` now appear as
  reels, the story ring and Instagram-style highlight circles rather than as
  separate archives.

Housekeeping
- Add @types/react; React was previously type-checked against its JavaScript
  source, so `npm run lint` gave almost no type safety on components.
- Vendor fonts and PWA icons locally; the app made third-party CDN requests
  despite advertising offline support and local-only processing.
- Drop unused better-sqlite3 (a native module that broke `npm install`).
- Add vitest with 36 tests over the filename and directory-naming rules.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011uBWhwV3wFQ5MBCcMHHem7

src/components/ArchiveDashboard.tsx

@@ -6,15 +6,15 @@ import {
   Trash2, 
   Zap 
 } from 'lucide-react';
-import { ServerArchive } from '../types';
+import { CacheData, ServerArchive } from '../types';
 
 interface ArchiveDashboardProps {
   archives: ServerArchive[];
-  localArchives?: any[];
+  localArchives?: CacheData[];
   cachedArchives: Set<string>;
   onSelect: (archive: ServerArchive) => void;
   onLocalSelect: () => void;
-  onLocalCacheSelect: (archive: any) => void;
+  onLocalCacheSelect: (archive: CacheData) => void;
   onClearCache: (name: string) => void;
   isScanning: boolean;
 }
@@ -85,7 +85,11 @@ export const ArchiveDashboard: React.FC<ArchiveDashboardProps> = ({
                 </div>
                 <div className="p-4 space-y-1">
                   <span className="font-bold text-sm block truncate uppercase tracking-tight text-black/80">{archive.name}</span>
-                  <span className="text-[10px] text-gray-400 uppercase tracking-widest">{archive.fileCount} items</span>
+                  <span className="text-[10px] text-gray-400 uppercase tracking-widest">
+                    {archive.fileCount === null
+                      ? `${archive.sources?.length ?? 1} source${(archive.sources?.length ?? 1) === 1 ? '' : 's'}`
+                      : `${archive.fileCount} items`}
+                  </span>
                 </div>
               </button>