Log to a file instead of only stdout

All app and uvicorn logging now goes to logs/app.log (rotating,
10MB x5), and a catch-all exception handler logs full tracebacks there
before returning a generic 500 — so an error is traceable to its cause
without depending on how the process was launched. logs/ is gitignored,
like the other runtime artifacts.

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

.gitignore

@@ -6,3 +6,4 @@ __pycache__/
 master.xprv.enc
 .pytest_cache/
 *.egg-info/
+logs/

app/logging_config.py

@@ -0,0 +1,28 @@
+import logging
+from logging.handlers import RotatingFileHandler
+from pathlib import Path
+
+LOG_DIR = Path(__file__).resolve().parent.parent / "logs"
+LOG_FILE = LOG_DIR / "app.log"
+
+_FORMAT = "%(asctime)s %(levelname)s [%(name)s] %(message)s"
+
+
+def setup_logging() -> None:
+    """Route all app + uvicorn logging to logs/app.log so errors are traceable
+    without depending on however the process happens to be launched."""
+    LOG_DIR.mkdir(exist_ok=True)
+
+    handler = RotatingFileHandler(LOG_FILE, maxBytes=10 * 1024 * 1024, backupCount=5)
+    handler.setFormatter(logging.Formatter(_FORMAT))
+
+    root = logging.getLogger()
+    root.setLevel(logging.INFO)
+    root.addHandler(handler)
+
+    # "uvicorn.error"/"uvicorn.access" have propagate=False in uvicorn's default
+    # logging config, so they never reach the root handler above and need their
+    # own. The parent "uvicorn" logger is deliberately skipped: uvicorn.error
+    # already bubbles into it, so attaching there too would double every line.
+    for logger_name in ("uvicorn.error", "uvicorn.access"):
+        logging.getLogger(logger_name).addHandler(handler)

app/main.py

@@ -1,10 +1,15 @@
 import asyncio
+import logging
 from contextlib import asynccontextmanager
 
-from fastapi import FastAPI
+from fastapi import FastAPI, Request
-from fastapi.responses import FileResponse
+from fastapi.responses import FileResponse, JSONResponse
 from fastapi.staticfiles import StaticFiles
 
+from app.logging_config import setup_logging
+
+setup_logging()
+
 import app.bets.confirmation  # noqa: F401  (registers the "bet" confirmation handler)
 import app.rounds.confirmation  # noqa: F401  (registers the "payout" confirmation handler)
 import app.withdrawals.confirmation  # noqa: F401  (registers the "withdrawal" confirmation handler)
@@ -22,6 +27,8 @@ from app.tx.broadcast import RbfBumper
 from app.tx.confirmation import ConfirmationPoller
 from app.tx.locks import UserLocks
 
+logger = logging.getLogger(__name__)
+
 
 def _make_electrum_client() -> ElectrumClient:
     return ElectrumClient(settings.electrum_host, settings.electrum_port, settings.electrum_use_ssl)
@@ -60,6 +67,12 @@ app.include_router(withdrawals_router)
 app.include_router(admin_router)
 
 
+@app.exception_handler(Exception)
+async def log_unhandled_exception(request: Request, exc: Exception) -> JSONResponse:
+    logger.exception("Unhandled error on %s %s", request.method, request.url.path)
+    return JSONResponse(status_code=500, content={"detail": "internal server error"})
+
+
 @app.get("/health")
 async def health() -> dict[str, str]:
     return {"status": "ok"}