refactor: enforce canonical backend imports

app/backend/features/screener/compiler.py

@@ -4,7 +4,7 @@ import json
 from typing import Any
 
 from backend.llm import transport as llm_transport
-from screener import FACTOR_FIELDS, REGIMES
+from backend.features.screener.engine import FACTOR_FIELDS, REGIMES
 
 
 class LLMCompilerError(RuntimeError):

app/backend/features/screener/engine.py

@@ -8,11 +8,11 @@ from collections import defaultdict
 from datetime import datetime, timedelta
 from typing import Any
 
-from advanced_strategies import ADVANCED_CURATED_STRATEGIES
 from backend.data.numbers import finite_number as _number
+from backend.data.providers.tushare_client import TushareClient, TushareError
+from backend.features.screener.strategies import ADVANCED_CURATED_STRATEGIES
 from database import ReviewDatabase
 from backend.features.sentiment.engine import build_sentiment_history, latest_contiguous_history
-from tushare_client import TushareClient, TushareError
 
 
 REGIMES = {