Rebuild position history from Binance fills

Sync account fills into a new trading_fills table every 60s and
reconstruct closed positions from them, so positions opened outside
the program are included and external closes get an exit price.
Positions link to plans by order id. The history drawer gains symbol,
close-date, outcome and source filters, a summary bar and pagination.

backend/src/alphapulse/models/__init__.py

@@ -2,7 +2,7 @@ from alphapulse.core.db import Base
 from alphapulse.models.ai import AiProvider, ChatMessage, ChatSession, ContextVersion, SkillNode, SkillVersion
 from alphapulse.models.market import Kline, KlineSyncState, MarketSymbol
 from alphapulse.models.news import CrawlLog, CrawlRun, NewsItem, NewsRevision, RawBody, RawResponse, Source
-from alphapulse.models.trading import TradingAccount, TradingAnalysis, TradingEvent, TradingOrder, TradingSymbol
+from alphapulse.models.trading import TradingAccount, TradingAnalysis, TradingEvent, TradingFill, TradingOrder, TradingSymbol
 
 __all__ = [
     "AiProvider",
@@ -25,6 +25,7 @@ __all__ = [
     "TradingAccount",
     "TradingAnalysis",
     "TradingEvent",
+    "TradingFill",
     "TradingOrder",
     "TradingSymbol",
 ]