fix: return retryable event stream upstream failures (#67)

src/main.py

@@ -124,3 +124,13 @@ async def event_stream():
                 )
             },
         )
+    except Exception:
+        return JSONResponse(
+            {"error": "Gitea event stream is temporarily unavailable"},
+            status_code=503,
+            headers={
+                "Retry-After": str(
+                    max(1, math.ceil(EVENT_STREAM_TIMEOUT_SECONDS))
+                )
+            },
+        )