feat: Deterministic MC checking — ALL controls, no LLM, reproducible

Replaced LLM-based MC verification with deterministic keyword matching:
- Extracts keywords from pass_criteria/fail_criteria
- Matches against document text via regex (case-insensitive)
- PASS if >= 60% of criteria keywords found AND no fail_criteria triggered
- Same text + same MCs = same result every time

Checks ALL MCs for the doc_type (max_controls=0):
- DSE: all 571 controls checked in <1 second
- Impressum: all 75 controls
- Cookie: all 381 controls

No LLM calls needed — purely deterministic keyword matching.
Bigram extraction for compound terms (e.g. "standardvertragsklauseln").
Stop word filtering for German legal text.

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

backend-compliance/compliance/api/agent_doc_check_routes.py

@@ -288,7 +288,7 @@ async def _check_single_document(entry: DocCheckEntry) -> list[DocCheckResult]:
             try:
                 from compliance.services.rag_document_checker import check_document_with_controls
                 mc_results = await check_document_with_controls(
-                    doc_text, entry.doc_type, entry.label, max_controls=15,
+                    doc_text, entry.doc_type, entry.label, max_controls=0,
                 )
                 if mc_results:
                     # Add MC results as additional checks to the main result