Add private Prometheus API metrics and Grafana performance dashboard

backend/app/main.py

@@ -44,6 +44,7 @@ from .logging_config import (
     summarize_http_body,
 )
 from .runtime import get_runtime_settings
+from .metrics import record_api, start_metrics
 
 logger = logging.getLogger(__name__)
 _background_tasks: list[asyncio.Task[None]] = []
@@ -112,6 +113,7 @@ async def log_requests_and_add_security_headers(request: Request, call_next):
         response = await call_next(request)
     except Exception:
         duration_ms = round((time.perf_counter() - started_at) * 1000, 2)
+        record_api(request, 500, time.perf_counter() - started_at)
         logger.exception(
             "request failed method=%s path=%s duration_ms=%s",
             request.method,
@@ -125,6 +127,7 @@ async def log_requests_and_add_security_headers(request: Request, call_next):
         raise
 
     duration_ms = round((time.perf_counter() - started_at) * 1000, 2)
+    record_api(request, response.status_code, time.perf_counter() - started_at)
     response.headers.setdefault("X-Request-ID", request_id)
     response.headers.setdefault("X-Content-Type-Options", "nosniff")
     response.headers.setdefault("X-Frame-Options", "DENY")
@@ -221,6 +224,7 @@ def _enforce_secure_startup_configuration() -> None:
 
 @app.on_event("startup")
 async def startup() -> None:
+    start_metrics()
     configure_logging(
         settings.log_level,
         settings.log_file,