feat: modularize scanner, enhance carousel preloading, and improve PWA updates

Summary of changes:
- Extracted archive scanning logic into a modular 'useArchiveScanner' hook for better maintainability and performance.
- Refined PostModal carousel with intelligent media preloading and smoother, jitter-free transitions.
- Optimized image rendering with 'decoding=async' and removed 'black flashes' between slide changes.
- Updated PWA configuration to 'autoUpdate' with hourly periodic checks for fresh content.
- Fixed several bugs including stories sorting, permalink parameter cleanup, and profile metadata cache restoration.
- Comprehensive updates to documentation (README.md and GEMINI.md) reflecting the new architecture.

src/lib/archive-files.ts

@@ -0,0 +1,36 @@
+import { ArchiveFile } from '../types';
+
+export class LocalArchiveFile implements ArchiveFile {
+  constructor(private file: File) {}
+  get name() { return this.file.name; }
+  get webkitRelativePath() { return this.file.webkitRelativePath; }
+  get size() { return this.file.size; }
+  text() { return this.file.text(); }
+  arrayBuffer() { return this.file.arrayBuffer(); }
+  stream() { return this.file.stream(); }
+}
+
+export class RemoteArchiveFile implements ArchiveFile {
+  constructor(
+    public name: string,
+    public webkitRelativePath: string,
+    public size: number,
+    public url: string
+  ) {}
+  async text() {
+    const res = await fetch(this.url);
+    return res.text();
+  }
+  async arrayBuffer() {
+    const res = await fetch(this.url);
+    return res.arrayBuffer();
+  }
+  stream() {
+    const transform = new TransformStream();
+    fetch(this.url).then(res => {
+      if (res.body) res.body.pipeTo(transform.writable);
+      else transform.writable.getWriter().close();
+    });
+    return transform.readable;
+  }
+}