Observability: Prometheus metrics, log panel, runbook

- GET /api/metrics renders Prometheus text (equity, P&L, per-strategy
  equity/pnl/allocation/halted, info) with no client library.
- In-memory ring log handler (app/logs.py) exposed at GET /api/logs and a
  dashboard "Server logs" panel; Runtime mirrors bot events into the logger.
- docs/runbook.md covers deploys, the kill switch, resetting paper state and
  going live. Adds tests for metrics rendering and the log ring.

backend/app/runtime.py

@@ -32,6 +32,15 @@ from app.store import Store
 
 logger = logging.getLogger(__name__)
 
+_LOG_LEVELS = {
+    "debug": logging.DEBUG,
+    "info": logging.INFO,
+    "trade": logging.INFO,
+    "warning": logging.WARNING,
+    "error": logging.ERROR,
+    "critical": logging.CRITICAL,
+}
+
 FeedFactory = Callable[[Settings], MarketData]
 BrokerFactory = Callable[[Settings], Broker]
 NotifierFactory = Callable[[Settings], Notifier | None]
@@ -91,8 +100,15 @@ class Runtime:
             with suppress(asyncio.QueueFull):
                 queue.put_nowait(payload)
         if payload.get("type") == "event":
+            self._log_event(payload["data"])
             self._maybe_notify(payload["data"])
 
+    def _log_event(self, event: dict[str, Any]) -> None:
+        """Mirror bot events into the logger so the dashboard log view is useful."""
+        level = str(event.get("level", "info")).lower()
+        message = event.get("message", "")
+        logger.log(_LOG_LEVELS.get(level, logging.INFO), "%s", message)
+
     def _maybe_notify(self, event: dict[str, Any]) -> None:
         if event.get("level") not in self.notify_levels:
             return