Fix pause bugs, faster stall retry

- Pause now aborts active extractions (previously extraction continued
  during pause, showing wrong status like Provider-Cooldown)
- Unpause clears provider circuit breaker for fresh start
- Post-processing status checks account for global pause state
- Reduce stall detection timeout from 30s to 15s for faster retry
- Reduce stall retry base delay from 500ms to 300ms

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "real-debrid-downloader",
-  "version": "1.5.20",
+  "version": "1.5.21",
   "description": "Real-Debrid Downloader Desktop (Electron + React + TypeScript)",
   "main": "build/main/main/main.js",
   "author": "Sucukdeluxe",