Availability requests hangs

### StatGPT SDMX Proxy version

0.3.0

### What steps will reproduce the bug?

call
curl --location '/statgpt/sdmx-proxy/api/v0/sdmx/3.0/availability/dataflow/IMF.STA/MFS_CBS/24.0.0' \
--header 'Content-Type: application/json' \
--data '{
"filters": []
}'

see
2026-06-18T09:40:41,098 INFO trace_id: c20e5afa95c55d27982e67539fb64601 span_id=65836b77c29cae90 [http-nio-8050-exec-49] i.s.u.c.i.SdmxSourceReadableDataLocationFactory: Limit hit on getting ReadableDataLocation, overflow to tmp URI

probably buffer overflow

### What is the expected behavior?

_No response_

### What do you see instead?

request hangs

### Additional information

_No response_

Reproduce the hang with the documented curl request to the /statgpt/sdmx-proxy/api/v0/sdmx/3.0/availability/dataflow/IMF.STA/MFS_CBS/24.0.0 endpoint and review the reported ReadableDataLocationFactory log entry. Trace the availability request from that endpoint, then verify that the request completes instead of hanging and that the overflow-to-tmp condition is handled.

Written by the indexing model from the issue text.