feat: multi-browser pooling (2 Chromium instances × 8 pages)

- Launch BROWSER_COUNT separate Chromium instances (default: 2)
- Each with PAGES_PER_BROWSER pages (default: 8, 16 total)
- Round-robin distribution across browser instances
- Independent restart scheduling per browser
- Updated health endpoint to show per-browser stats
- docker-compose: added BROWSER_COUNT and PAGES_PER_BROWSER env vars

docker-compose.yml

@@ -17,10 +17,13 @@ services:
       - PRO_KEYS=${PRO_KEYS}
       - SMTP_HOST=host.docker.internal
       - SMTP_PORT=25
+      - POOL_SIZE=15
+      - BROWSER_COUNT=2
+      - PAGES_PER_BROWSER=8
     volumes:
       - docfast-data:/app/data
-    mem_limit: 512m
-    cpus: 1.0
+    mem_limit: 2560m
+    cpus: 1.5
 
 volumes:
   docfast-data: