fix: 3 bugs — synthesis crash, stale running cycle, invalid tickers

- knowledge.py: trade_line crash when pnl_pct is None in dict
  (t.get('pnl_pct',0) returns None if key exists with None value — use 'or 0')
- database.py: cleanup_stale_running_cycles() marks any 'running' cycle
  as 'error' on startup (uvicorn reload mid-cycle left status stuck)
- main.py: call cleanup_stale_running_cycles() at startup with warning log
- database.py: _normalize_ticker() converts GPT-4o exchange:symbol format
  (NSE:RELIANCE → RELIANCE.NS, BSE:X → X.BO, etc.) so yfinance stops
  spamming 404 errors for every MTM request

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/knowledge.py

@@ -64,8 +64,9 @@ Note timing: {timing[:150]}
 
     def trade_line(t):
         mat = t.get("maturity", {})
+        pnl = t.get("pnl_pct") or 0
         return (f"{t.get('underlying','?')} {t.get('strategy','?')} "
-                f"P&L={t.get('pnl_pct',0):+.1f}% score={t.get('latest_score','?')} "
+                f"P&L={pnl:+.1f}% score={t.get('latest_score','?')} "
                 f"regime={t.get('macro_regime','?')} [{mat.get('readable','')}]")
 
     trades_block = f"""