feat(prospecting): add content scraping for POC builder (Workstream 3A)

- New scrape_content() method in enrichment_service: extracts meta
  description, H1/H2 headings, paragraphs, images (filtered for size),
  social links, service items, and detected languages using BeautifulSoup
- Scans 6 pages per prospect: /, /about, /a-propos, /services,
  /nos-services, /contact
- Results stored as JSON in prospect.scraped_content_json
- New endpoints: POST /content-scrape/{id} and /content-scrape/batch
- Added to full_enrichment pipeline (Step 5, before security audit)
- CONTENT_SCRAPE job type for scan-jobs tracking
- "Content Scrape" batch button on scan-jobs page
- Add beautifulsoup4 to requirements.txt

Tested on batirenovation-strasbourg.fr: extracted 30 headings,
21 paragraphs, 13 images.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/prospecting/services/prospect_service.py

@@ -251,6 +251,17 @@ class ProspectService:
             .all()
         )
 
+    def get_pending_content_scrape(self, db: Session, limit: int = 100) -> list[Prospect]:
+        return (
+            db.query(Prospect)
+            .filter(
+                Prospect.has_website.is_(True),
+                Prospect.last_content_scrape_at.is_(None),
+            )
+            .limit(limit)
+            .all()
+        )
+
     def get_pending_security_audit(self, db: Session, limit: int = 50) -> list[Prospect]:
         return (
             db.query(Prospect)