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/metrics.py

@@ -0,0 +1,96 @@
+from __future__ import annotations
+
+from app.schemas import MultiStatusOut
+
+# Rendered as Prometheus text exposition format (no client library needed).
+# The route serves this at GET /api/metrics for the existing Prometheus scrape.
+
+
+def _escape(value: str) -> str:
+    return value.replace("\\", "\\\\").replace('"', '\\"')
+
+
+def _metric(
+    name: str, help_text: str, value: float | int, labels: dict[str, str] | None = None
+) -> str:
+    lines = [f"# HELP {name} {help_text}", f"# TYPE {name} gauge"]
+    if labels:
+        rendered = ",".join(f'{k}="{_escape(v)}"' for k, v in labels.items())
+        lines.append(f"{name}{{{rendered}}} {value}")
+    else:
+        lines.append(f"{name} {value}")
+    return "\n".join(lines)
+
+
+def render_metrics(status: MultiStatusOut, mode: str, exchange: str) -> str:
+    """Render the current portfolio state as Prometheus metrics."""
+    parts = [
+        _metric("crypto_running", "1 when the bot is running", int(status.running)),
+        _metric("crypto_equity", "Total account equity", status.equity),
+        _metric("crypto_starting_balance", "Starting balance", status.starting_balance),
+        _metric("crypto_total_pnl", "Total profit and loss", status.total_pnl),
+        _metric(
+            "crypto_open_positions",
+            "Number of open positions across strategies",
+            sum(s.open_positions for s in status.strategies),
+        ),
+        _metric(
+            "crypto_strategies",
+            "Number of configured strategies",
+            len(status.strategies),
+        ),
+    ]
+
+    if status.price is not None:
+        parts.append(_metric("crypto_price", "Latest mark price", status.price))
+
+    # Common labels shared by the per-strategy families.
+    lines = [
+        "# HELP crypto_strategy_equity Equity per strategy",
+        "# TYPE crypto_strategy_equity gauge",
+    ]
+    for s in status.strategies:
+        labels = {"strategy": s.strategy_key, "symbol": s.symbol}
+        rendered = ",".join(f'{k}="{_escape(v)}"' for k, v in labels.items())
+        lines.append(f"crypto_strategy_equity{{{rendered}}} {s.equity}")
+    parts.append("\n".join(lines))
+
+    lines = [
+        "# HELP crypto_strategy_pnl Total P&L per strategy",
+        "# TYPE crypto_strategy_pnl gauge",
+    ]
+    for s in status.strategies:
+        labels = {"strategy": s.strategy_key, "symbol": s.symbol}
+        rendered = ",".join(f'{k}="{_escape(v)}"' for k, v in labels.items())
+        lines.append(f"crypto_strategy_pnl{{{rendered}}} {s.total_pnl}")
+    parts.append("\n".join(lines))
+
+    lines = [
+        "# HELP crypto_strategy_allocation Fraction of the balance per strategy",
+        "# TYPE crypto_strategy_allocation gauge",
+    ]
+    for s in status.strategies:
+        labels = {"strategy": s.strategy_key}
+        rendered = ",".join(f'{k}="{_escape(v)}"' for k, v in labels.items())
+        lines.append(f"crypto_strategy_allocation{{{rendered}}} {s.allocation}")
+    parts.append("\n".join(lines))
+
+    lines = [
+        "# HELP crypto_strategy_halted 1 when a strategy is halted",
+        "# TYPE crypto_strategy_halted gauge",
+    ]
+    for s in status.strategies:
+        labels = {"strategy": s.strategy_key}
+        rendered = ",".join(f'{k}="{_escape(v)}"' for k, v in labels.items())
+        lines.append(f"crypto_strategy_halted{{{rendered}}} {int(s.halted)}")
+    parts.append("\n".join(lines))
+
+    info_labels = {"mode": mode, "exchange": exchange}
+    rendered = ",".join(f'{k}="{_escape(v)}"' for k, v in info_labels.items())
+    parts.append(
+        "# HELP crypto_info Build information\n"
+        "# TYPE crypto_info gauge\n"
+        f"crypto_info{{{rendered}}} 1"
+    )
+
+    return "\n".join(parts) + "\n"