fix(llm): add fetch-models endpoint, fix SQL Lab INSERT (client_id truncation, sync mode, target_column, timestamp normalization)

- Add POST /api/llm/providers/fetch-models route with LLMClient.fetch_models()
- Add target_column to TranslationJob model/schema/service/orchestrator
- Fix SQL Lab execute: truncate client_id to 11 chars (varchar(11))
- Switch SQL Lab to sync mode (runAsync: false) — no Celery workers
- Fix polling: unwrap nested result from Superset query API
- Fix ClickHouse timestamp: normalize float timestamps to YYYY-MM-DD

backend/tests/services/dataset_review/test_superset_matrix.py

@@ -1,5 +1,4 @@
 # [DEF:SupersetCompatibilityMatrixTests:Module]
-# @COMPLEXITY: 3
 # @SEMANTICS: dataset_review, superset, compatibility_matrix, preview, sql_lab, tests
 # @PURPOSE: Verifies Superset preview and SQL Lab endpoint fallback strategy used by dataset-review orchestration.
 # @LAYER: Tests
@@ -21,7 +20,6 @@ from src.core.utils.superset_compilation_adapter import (
 
 
 # [DEF:make_adapter:Function]
-# @COMPLEXITY: 2
 # @PURPOSE: Build an adapter with a mock Superset client and deterministic environment for compatibility tests.
 # @RELATION: [DEPENDS_ON] ->[SupersetCompilationAdapter]
 def make_adapter():
@@ -43,7 +41,6 @@ def make_adapter():
 
 
 # [DEF:test_preview_prefers_supported_client_method_before_network_fallback:Function]
-# @COMPLEXITY: 2
 # @PURPOSE: Confirms preview compilation uses a supported client method first when the capability exists.
 # @RELATION: [DEPENDS_ON] ->[SupersetCompilationAdapter]
 def test_preview_prefers_supported_client_method_before_network_fallback():
@@ -69,7 +66,6 @@ def test_preview_prefers_supported_client_method_before_network_fallback():
 
 
 # [DEF:test_preview_falls_back_across_matrix_until_supported_endpoint_returns_sql:Function]
-# @COMPLEXITY: 3
 # @PURPOSE: Confirms preview fallback walks the compatibility matrix from preferred to legacy endpoints until one returns compiled SQL.
 # @RELATION: [DEPENDS_ON] ->[SupersetCompilationAdapter]
 def test_preview_falls_back_across_matrix_until_supported_endpoint_returns_sql():
@@ -104,7 +100,6 @@ def test_preview_falls_back_across_matrix_until_supported_endpoint_returns_sql()
 
 
 # [DEF:test_sql_lab_launch_falls_back_to_legacy_execute_endpoint:Function]
-# @COMPLEXITY: 3
 # @PURPOSE: Confirms SQL Lab launch falls back from modern to legacy execute endpoint and preserves canonical session reference extraction.
 # @RELATION: [DEPENDS_ON] ->[SupersetCompilationAdapter]
 def test_sql_lab_launch_falls_back_to_legacy_execute_endpoint():