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_log_persistence.py

@@ -3,7 +3,6 @@
 # @SEMANTICS: test, log, persistence, unit_test
 # @PURPOSE: Unit tests for TaskLogPersistenceService.
 # @LAYER: Test
-# @COMPLEXITY: 5
 
 # [SECTION: IMPORTS]
 from datetime import datetime
@@ -20,7 +19,6 @@ from src.core.task_manager.models import LogEntry, LogFilter
 # [DEF:TestLogPersistence:Class]
 # @RELATION: BINDS_TO -> test_log_persistence
 # @PURPOSE: Test suite for TaskLogPersistenceService.
-# @COMPLEXITY: 5
 # @TEST_DATA: log_entry -> {"task_id": "test-task-1", "level": "INFO", "source": "test_source", "message": "Test message"}
 class TestLogPersistence: