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/test_dashboards_api.py

@@ -1,6 +1,5 @@
 # [DEF:TestDashboardsApi:Module]
 # @RELATION: VERIFIES ->[src.api.routes.dashboards]
-# @COMPLEXITY: 3
 # @PURPOSE: Comprehensive contract-driven tests for Dashboard Hub API
 # @LAYER: Domain (Tests)
 # @SEMANTICS: tests, dashboards, api, contract, remediation
@@ -561,7 +560,7 @@ def test_backup_dashboards_with_schedule(mock_deps):
 # --- 8. Internal logic: _task_matches_dashboard ---
 # [/DEF:test_backup_dashboards_with_schedule:Function]
 
-from src.api.routes.dashboards import _task_matches_dashboard
+from src.api.routes.dashboards._projection import _task_matches_dashboard
 
 
 # [DEF:test_task_matches_dashboard_logic:Function]