fix(critical): remove dead manifold.get_probability() from legacy scan and fix BUY_NO payout calculation

- Legacy scan called ManifoldClient.get_probability(), removed in the v3
  matcher migration, causing AttributeError when positions had changed
  family keys. The block used Manifold to escalate positions to
  CLOSE_RECOMMENDED (inversion detection) — a trading decision forbidden
  under MANIFOLD_SIGNAL_ENABLED=false — so the dependency is removed
  entirely; the scan keeps family re-keying and sibling-conflict logic.

- PaperExecutor.close_position() computed cash += position_cost * resolution,
  ignoring direction: a winning BUY_NO (resolution=0.0) paid out $0 and
  reported a loss. Now settles per trade:
    BUY_YES: payout = shares * resolution
    BUY_NO:  payout = shares * (1 - resolution)
  with pnl = payout - net_cost; Telegram win/loss keys off pnl > 0.
  Adds read-only Database.get_open_trades_for_market().

- tests/test_paper_close.py covers the 4 deterministic payout cases;
  tests/conftest.py shims datetime.UTC for local Python 3.10 (prod is 3.11).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bot/data/db.py

@@ -152,6 +152,20 @@ class Database:
             """)
             return [dict(r) for r in rows]
 
+    async def get_open_trades_for_market(self, market_id: str) -> list[dict]:
+        """Return direction, shares and net_cost for each open trade in a market.
+
+        Used by PaperExecutor.close_position() to compute the settlement
+        payout per direction (BUY_NO pays out when resolution = 0.0).
+        """
+        async with self._pool.acquire() as conn:
+            rows = await conn.fetch(
+                "SELECT direction, shares, net_cost FROM trades "
+                "WHERE market_id = $1 AND closed_at IS NULL",
+                market_id,
+            )
+            return [dict(r) for r in rows]
+
     async def close_paper_position(
         self, market_id: str, reason: str = "", resolution: Optional[float] = None
     ) -> None: