* fix(relay): bound internal reserve request bodies
* fix(relay): authorize before reading reserve bodies
Hono reads a chunked body inside the body limit before next(). A caller who fails the director check can no longer stall the refusal, and an oversized body from that caller is not reported as 413.
* test(relay): cover an unavailable demote body
The missing-route check only posted to /internal/reserve. Demote now gets the same oversized request and must stay 404.
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Co-authored-by: Neil <neil@stably.ai>