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/types/index.ts

@@ -0,0 +1,36 @@
+export interface MediaFile {
+  name: string;
+  url: string;
+  type: 'image' | 'video';
+  index: number;
+}
+
+export interface Post {
+  id: string;
+  date: string;
+  username: string;
+  caption: string;
+  media: MediaFile[];
+  thumbnail: string;
+  isStory?: boolean;
+}
+
+/**
+ * Common interface for both local File objects and remote server-side files.
+ */
+export interface ArchiveFile {
+  name: string;
+  webkitRelativePath: string;
+  size: number;
+  text(): Promise<string>;
+  arrayBuffer(): Promise<ArrayBuffer>;
+  stream(): ReadableStream<Uint8Array>;
+  url?: string;
+}
+
+export interface ServerArchive {
+  name: string;
+  thumbnail: string;
+  path: string;
+  fileCount: number;
+}