feat(multi-layer): complete Multi-Layer Control Architecture (Phases 1-8 + Pass 0)

Implements the full Multi-Layer Control Architecture for migrating ~25,000
Rich Controls into atomic, deduplicated Master Controls with full traceability.

Architecture: Legal Source → Obligation → Control Pattern → Master Control → Customer Instance

New services:
- ObligationExtractor: 3-tier extraction (exact → embedding → LLM)
- PatternMatcher: 2-tier matching (keyword + embedding + domain-bonus)
- ControlComposer: Pattern + Obligation → Master Control
- PipelineAdapter: Pipeline integration + Migration Passes 1-5
- DecompositionPass: Pass 0a/0b — Rich Control → atomic Controls
- CrosswalkRoutes: 15 API endpoints under /v1/canonical/

New DB schema:
- Migration 060: obligation_extractions, control_patterns, crosswalk_matrix
- Migration 061: obligation_candidates, parent_control_uuid tracking

Pattern Library: 50 YAML patterns (30 core + 20 IT-security)
Go SDK: Pattern loader with YAML validation and indexing
Documentation: MkDocs updated with full architecture overview

500 Python tests passing across all components.

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

backend-compliance/compliance/api/__init__.py

@@ -53,6 +53,7 @@ _ROUTER_MODULES = [
     "wiki_routes",
     "canonical_control_routes",
     "control_generator_routes",
+    "crosswalk_routes",
     "process_task_routes",
     "evidence_check_routes",
 ]