fix: browser UA for scraper, Qdrant healthcheck endpoint

Scraper was using a bot User-Agent that triggered Cloudflare bot
detection, returning challenge pages with < 100 chars of content.
Switched to a standard Chrome UA with Accept headers.

Qdrant healthcheck used /healthz which does not exist in v1.9.0.
Changed to GET / which is always available. Added start_period: 30s
so the check does not fire before Qdrant has time to initialise.
Added --debug flag to scraper for future extraction diagnostics.

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

docker-compose.yml

@@ -29,10 +29,11 @@ services:
     networks:
       - rag_net
     healthcheck:
-      test: ["CMD", "curl", "-f", "http://localhost:6333/healthz"]
-      interval: 30s
+      test: ["CMD", "curl", "-sf", "http://localhost:6333/"]
+      interval: 15s
       timeout: 10s
-      retries: 3
+      retries: 5
+      start_period: 30s
 
   rag-api:
     build: .