Address the rate-limit flood and secondary errors seen during large
recipe ingestion (example-images directory import):
- batch import: share one adaptive-concurrency semaphore across the whole
batch (previously each item got a fresh semaphore, so the min/max
concurrency bounds never applied and every item ran concurrently);
synchronize the shared semaphore capacity after each completed item.
- comfy parser: guard ckpt_name against list/None values so re.search no
longer raises TypeError and fails the whole image import.
- civarchive client: normalize empty-string failure payloads to
"Request failed" and treat a missing payload as an error, fixing the
"'NoneType' object has no attribute 'get'" crash.
- civarchive client: log connectivity-guard offline-cooldown
short-circuits at DEBUG instead of one ERROR per request.
Will Miao