refactor(schema): bind requests to one serving schema

What does this MR do and why?

Requests share one ontology snapshot instead of keeping separate service-owned copies. Serving behavior stays unchanged; active-archive switching is a separate follow-up.

Related Issues

Relates to #184 (closed). Part 1 of 2 replacing !2452 (closed). Follow-up: !2459 (merged).

Testing

252 server unit tests and 18 integration checks passed locally, along with Clippy and formatting.

Performance Analysis

• This merge request does not introduce any performance regression. If a performance regression is expected, explain why.

Agent context

No watcher, readiness, deadline, startup, or documentation changes. Not benchmarked.