feat: Multi-URL Document Check with full checklist visibility

New "Dokumenten-Pruefung" tab in Compliance Agent:
- User adds multiple URLs with document type (DSI, AGB, Impressum, Cookie, Widerruf)
- Each document loaded via Playwright, accordions expanded, text extracted
- Checked against type-specific legal checklist
- Optional: Cookie banner check via checkbox

Checklisten-UX (solves "100% looks like nothing was checked"):
- All checks shown per document: green checkmark + matched text excerpt
- Red X for missing fields with legal reference
- Builds user trust: "9 Punkte geprueft, alle bestanden"
- Expandable per document with completeness bar

New checklists:
- Impressum: §5 TMG (6 fields: name, address, contact, register, VAT, representative)
- Cookie-Richtlinie: §25 TDDDG (5 fields: types, purposes, retention, third-party, opt-out)

Backend:
- POST /agent/doc-check — async with polling (same pattern as /scan)
- DocCheckResult includes checks[] with passed/failed + matched_text
- dsi_document_checker returns all_checks in SCORE finding
- Email report shows per-document checklist

Files: agent_doc_check_routes.py (280 LOC), DocCheckTab.tsx (248 LOC),
ChecklistView.tsx (130 LOC), dsi_document_checker.py (+70 LOC)

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

backend-compliance/main.py

@@ -45,6 +45,7 @@ from compliance.api.company_profile_routes import router as company_profile_rout
 from compliance.api.agent_notification_routes import router as agent_notify_router
 from compliance.api.agent_analyze_routes import router as agent_analyze_router
 from compliance.api.agent_scan_routes import router as agent_scan_router
+from compliance.api.agent_doc_check_routes import router as agent_doc_check_router
 
 # Middleware
 from middleware import (
@@ -144,6 +145,7 @@ app.include_router(company_profile_router, prefix="/api")
 app.include_router(agent_notify_router, prefix="/api")
 app.include_router(agent_analyze_router, prefix="/api")
 app.include_router(agent_scan_router, prefix="/api")
+app.include_router(agent_doc_check_router, prefix="/api")
 
 
 if __name__ == "__main__":