feat: trailing-stop auto-exit for paper trades + close/digest alerts

Applies the backtest-validated trailing stop to live paper trading, and surfaces
it transparently.

Exit (A):
- New paper-trade exit policy (paper_exit_mode=trailing, paper_trailing_pct=12),
  tunable in Admin → Paper-Trade Exit. resolve_open_trades runs a trailing stop
  (initial stop as floor, ratchets up from the peak; target ignored — the
  validated rule) and records close_reason (trailing|stop|target|manual; +migration
  013).
- list_trades enriches open trades with the live trailing-stop level + distance %.
  Open Trades panel shows the active tactic and a Trail Stop column.

Alerts (B):
- Daily digest now lists open trades with unrealized gain, trailing stop, and how
  far away it is.
- New "trade closed" alert: one summary per auto-close (trailing/target/stop, not
  manual) — direction, reason, days held, P&L abs+%/R — covering wins AND
  stop-loss losses. Deduped by trade id; toggle in Admin alerts.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/unit/test_alert_service.py

@@ -3,11 +3,13 @@
 from __future__ import annotations
 
 from datetime import date, datetime, timedelta, timezone
+from types import SimpleNamespace
 
 import pytest
 
 from app.models.alert import AlertLog
 from app.models.ohlcv import OHLCVRecord
+from app.models.paper_trade import PaperTrade
 from app.models.score import CompositeScore
 from app.models.sr_level import SRLevel
 from app.models.ticker import Ticker
@@ -168,3 +170,53 @@ async def test_dispatch_no_credentials(session):
     await svc.update_alert_config(session, enabled=True)  # enabled but no token/chat
     res = await svc.dispatch_alerts(session)
     assert res["status"] == "no_credentials"
+
+
+async def _add_closed_trade(session, symbol: str, reason: str, *,
+                            close: float = 110.0, closed_hours_ago: float = 1.0) -> None:
+    if await session.get(User, 1) is None:
+        session.add(User(id=1, username="u", password_hash="x", role="user", has_access=True))
+        await session.flush()
+    t = Ticker(symbol=symbol)
+    session.add(t)
+    await session.flush()
+    now = datetime.now(timezone.utc)
+    session.add(PaperTrade(
+        user_id=1, ticker_id=t.id, direction="long",
+        entry_price=100.0, shares=10.0, stop_loss=95.0, target=120.0,
+        status="closed", opened_at=now - timedelta(days=5),
+        close_price=close, closed_at=now - timedelta(hours=closed_hours_ago),
+        close_reason=reason,
+    ))
+    await session.commit()
+
+
+async def test_config_includes_trade_closed_toggle(session):
+    assert (await svc.get_alert_config(session))["trade_closed_enabled"] is True
+    cfg = await svc.update_alert_config(session, trade_closed_enabled=False)
+    assert cfg["trade_closed_enabled"] is False
+
+
+async def test_collect_closed_trades_filters_manual_and_old(session):
+    await _add_closed_trade(session, "WIN", "trailing", close=110.0, closed_hours_ago=1)
+    await _add_closed_trade(session, "MAN", "manual", close=110.0, closed_hours_ago=1)   # manual → skip
+    await _add_closed_trade(session, "OLD", "stop", close=95.0, closed_hours_ago=100)    # too old → skip
+
+    out = await svc._collect_closed_trades(session)
+    assert len(out) == 1
+    _, text = out[0]
+    assert "WIN" in text and "trailing stop" in text
+
+
+def test_format_closed_trade_win():
+    now = datetime.now(timezone.utc)
+    trade = SimpleNamespace(
+        direction="long", entry_price=100.0, close_price=110.0, shares=10.0,
+        stop_loss=95.0, opened_at=now - timedelta(days=12), closed_at=now,
+        close_reason="trailing",
+    )
+    txt = svc._format_closed_trade(trade, "AAA")
+    assert "✅" in txt           # win
+    assert "+10.0%" in txt
+    assert "+2.00R" in txt       # +10% over a 5% stop
+    assert "held 12d" in txt