test+docs: add policy library tests (67 tests) and MKDocs documentation

- New test_policy_templates.py: 67 tests covering all 29 policy types,
  API creation, filtering, placeholders, seed script validation
- Updated test_legal_template_routes.py: fix type count 16→52
- New MKDocs page policy-bibliothek.md with full template reference
- Updated dokumentengenerierung.md and rechtliche-texte.md with cross-refs
- Added policy-bibliothek to mkdocs.yml navigation

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

backend-compliance/tests/test_legal_template_routes.py

@@ -121,7 +121,7 @@ class TestLegalTemplateSchemas:
         assert d == {"status": "archived", "title": "Neue DSE"}
 
     def test_valid_document_types_constant(self):
-        """VALID_DOCUMENT_TYPES contains all 16 expected types (post-Migration 020)."""
+        """VALID_DOCUMENT_TYPES contains all 52 expected types (Migration 020+051+054)."""
         # Original types
         assert "privacy_policy" in VALID_DOCUMENT_TYPES
         assert "terms_of_service" in VALID_DOCUMENT_TYPES
@@ -141,7 +141,20 @@ class TestLegalTemplateSchemas:
         assert "cookie_banner" in VALID_DOCUMENT_TYPES
         assert "agb" in VALID_DOCUMENT_TYPES
         assert "clause" in VALID_DOCUMENT_TYPES
-        assert len(VALID_DOCUMENT_TYPES) == 16
+        # Security concepts (Migration 051)
+        assert "it_security_concept" in VALID_DOCUMENT_TYPES
+        assert "data_protection_concept" in VALID_DOCUMENT_TYPES
+        assert "backup_recovery_concept" in VALID_DOCUMENT_TYPES
+        assert "logging_concept" in VALID_DOCUMENT_TYPES
+        assert "incident_response_plan" in VALID_DOCUMENT_TYPES
+        assert "access_control_concept" in VALID_DOCUMENT_TYPES
+        assert "risk_management_concept" in VALID_DOCUMENT_TYPES
+        # Policy templates (Migration 054) — spot check
+        assert "information_security_policy" in VALID_DOCUMENT_TYPES
+        assert "data_protection_policy" in VALID_DOCUMENT_TYPES
+        assert "business_continuity_policy" in VALID_DOCUMENT_TYPES
+        # Total: 16 original + 7 security concepts + 29 policies = 52
+        assert len(VALID_DOCUMENT_TYPES) == 52
         # Old names must NOT be present after rename
         assert "data_processing_agreement" not in VALID_DOCUMENT_TYPES
         assert "withdrawal_policy" not in VALID_DOCUMENT_TYPES
@@ -488,9 +501,9 @@ class TestLegalTemplateSeed:
 class TestLegalTemplateNewTypes:
     """Validate new document types added in Migration 020."""
 
-    def test_all_16_types_present(self):
-        """VALID_DOCUMENT_TYPES has exactly 16 entries."""
-        assert len(VALID_DOCUMENT_TYPES) == 16
+    def test_all_52_types_present(self):
+        """VALID_DOCUMENT_TYPES has exactly 52 entries (16 + 7 security + 29 policies)."""
+        assert len(VALID_DOCUMENT_TYPES) == 52
 
     def test_new_types_are_valid(self):
         """All Migration 020 new types are accepted."""