feat(027): Final Phase T038-T043 implementation

- T038: SessionEvent logger and persistence logic
  - Added SessionEventLogger service with explicit audit event persistence
  - Added SessionEvent model with events relationship on DatasetReviewSession
  - Integrated event logging into orchestrator flows and API mutation endpoints

- T039: Semantic source version propagation
  - Added source_version column to SemanticFieldEntry
  - Added propagate_source_version_update() to SemanticResolver
  - Preserves locked/manual field invariants during propagation

- T040: Batch approval API and UI actions
  - Added batch semantic approval endpoint (/fields/semantic/approve-batch)
  - Added batch mapping approval endpoint (/mappings/approve-batch)
  - Added batch approval actions to SemanticLayerReview and ExecutionMappingReview components
  - Aligned batch semantics with single-item approval contracts

- T041: Superset compatibility matrix tests
  - Added test_superset_matrix.py with preview and SQL Lab fallback coverage
  - Tests verify client method preference and matrix fallback behavior

- T042: RBAC audit sweep on session-mutation endpoints
  - Added _require_owner_mutation_scope() helper
  - Applied owner guards to update_session, delete_session, and all mutation endpoints
  - Ensured no bypass of existing permission checks

- T043: i18n coverage for dataset-review UI
  - Added workspace state labels (empty/importing/review) to en.json and ru.json
  - Added batch action labels for semantics and mappings
  - Fixed workspace state comparison to lowercase strings
  - Removed hardcoded workspace state display strings

Signed-off-by: Implementation Specialist <impl@ss-tools>

backend/src/api/routes/__tests__/test_datasets.py

@@ -1,9 +1,9 @@
-# [DEF:backend.src.api.routes.__tests__.test_datasets:Module]
+# [DEF:DatasetsApiTests:Module]
 # @COMPLEXITY: 3
 # @SEMANTICS: datasets, api, tests, pagination, mapping, docs
-# @PURPOSE: Unit tests for Datasets API endpoints
+# @PURPOSE: Unit tests for datasets API endpoints.
 # @LAYER: API
-# @RELATION: TESTS -> backend.src.api.routes.datasets
+# @RELATION: DEPENDS_ON -> backend.src.api.routes.datasets
 # @INVARIANT: Endpoint contracts remain stable for success and validation failure paths.
 
 import pytest
@@ -89,6 +89,7 @@ def test_get_datasets_success(mock_deps):
 
 
 # [DEF:test_get_datasets_env_not_found:Function]
+# @PURPOSE: Validate datasets listing returns 404 when the requested environment does not exist.
 # @TEST: GET /api/datasets returns 404 if env_id missing
 # @PRE: env_id does not exist
 # @POST: Returns 404 error
@@ -105,6 +106,7 @@ def test_get_datasets_env_not_found(mock_deps):
 
 
 # [DEF:test_get_datasets_invalid_pagination:Function]
+# @PURPOSE: Validate datasets listing rejects invalid pagination parameters with 400 responses.
 # @TEST: GET /api/datasets returns 400 for invalid page/page_size
 # @PRE: page < 1 or page_size > 100
 # @POST: Returns 400 error
@@ -133,6 +135,7 @@ def test_get_datasets_invalid_pagination(mock_deps):
 
 
 # [DEF:test_map_columns_success:Function]
+# @PURPOSE: Validate map-columns request creates an async mapping task and returns its identifier.
 # @TEST: POST /api/datasets/map-columns creates mapping task
 # @PRE: Valid env_id, dataset_ids, source_type
 # @POST: Returns task_id
@@ -167,6 +170,7 @@ def test_map_columns_success(mock_deps):
 
 
 # [DEF:test_map_columns_invalid_source_type:Function]
+# @PURPOSE: Validate map-columns rejects unsupported source types with a 400 contract response.
 # @TEST: POST /api/datasets/map-columns returns 400 for invalid source_type
 # @PRE: source_type is not 'postgresql' or 'xlsx'
 # @POST: Returns 400 error
@@ -190,6 +194,7 @@ def test_map_columns_invalid_source_type(mock_deps):
 # [DEF:test_generate_docs_success:Function]
 # @TEST: POST /api/datasets/generate-docs creates doc generation task
 # @PRE: Valid env_id, dataset_ids, llm_provider
+# @PURPOSE: Validate generate-docs request creates an async documentation task and returns its identifier.
 # @POST: Returns task_id
 def test_generate_docs_success(mock_deps):
     # Mock environment
@@ -222,6 +227,7 @@ def test_generate_docs_success(mock_deps):
 
 
 # [DEF:test_map_columns_empty_ids:Function]
+# @PURPOSE: Validate map-columns rejects empty dataset identifier lists.
 # @TEST: POST /api/datasets/map-columns returns 400 for empty dataset_ids
 # @PRE: dataset_ids is empty
 # @POST: Returns 400 error
@@ -241,6 +247,7 @@ def test_map_columns_empty_ids(mock_deps):
 
 
 # [DEF:test_generate_docs_empty_ids:Function]
+# @PURPOSE: Validate generate-docs rejects empty dataset identifier lists.
 # @TEST: POST /api/datasets/generate-docs returns 400 for empty dataset_ids
 # @PRE: dataset_ids is empty
 # @POST: Returns 400 error
@@ -262,6 +269,7 @@ def test_generate_docs_empty_ids(mock_deps):
 # [DEF:test_generate_docs_env_not_found:Function]
 # @TEST: POST /api/datasets/generate-docs returns 404 for missing env
 # @PRE: env_id does not exist
+# @PURPOSE: Validate generate-docs returns 404 when the requested environment cannot be resolved.
 # @POST: Returns 404 error
 def test_generate_docs_env_not_found(mock_deps):
     """@PRE: env_id must be a valid environment."""
@@ -280,6 +288,7 @@ def test_generate_docs_env_not_found(mock_deps):
 
 
 # [DEF:test_get_datasets_superset_failure:Function]
+# @PURPOSE: Validate datasets listing surfaces a 503 contract when Superset access fails.
 # @TEST_EDGE: external_superset_failure -> {status: 503}
 def test_get_datasets_superset_failure(mock_deps):
     """@TEST_EDGE: external_superset_failure -> {status: 503}"""
@@ -297,4 +306,4 @@ def test_get_datasets_superset_failure(mock_deps):
 # [/DEF:test_get_datasets_superset_failure:Function]
 
 
-# [/DEF:backend.src.api.routes.__tests__.test_datasets:Module]
+# [/DEF:DatasetsApiTests:Module]