Async FS optimizations, exponential backoff, cleanup dedup and release v1.4.72

- Convert all sync FS ops (existsSync, readdirSync, statSync, writeFileSync,
  rmSync, renameSync) to async equivalents across download-manager, extractor,
  cleanup, storage, and logger to prevent UI freezes
- Replace linear retry delays with exponential backoff + jitter to prevent
  retry storms with many parallel downloads
- Deduplicate resolveArchiveItems into single shared function
- Replace Array.shift() O(N) in bandwidth chart with slice-based trimming
- Make logger rotation async in the async flush path

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "real-debrid-downloader",
-  "version": "1.4.71",
+  "version": "1.4.72",
   "description": "Real-Debrid Downloader Desktop (Electron + React + TypeScript)",
   "main": "build/main/main/main.js",
   "author": "Sucukdeluxe",