Enforce the rate limiter on submission entry points

[Meshmulla]

Summary

We have a rate_limiter module (soroban/src/rate_limiter.rs), but it doesn't appear to be enforced on the submission entry points. Wiring it in would protect against spam and abuse (e.g. a single operator flooding submissions) and make resource usage more predictable.

What we'd like

• Apply rate limiting to the submission / report entry points
• Make limits configurable (per-caller window and max count) by an admin role
• Reject over-limit calls with a clear, specific error

Where to look

• soroban/src/rate_limiter.rs — the limiter primitive
• soroban/src/submission_pause.rs, submission_replay.rs, report_hash.rs — submission-related flows to guard
• soroban/src/acl.rs — who can configure the limits

Acceptance criteria

• Submission entry points enforce the rate limiter
• Limits are admin-configurable (window + max)
• Over-limit calls revert with a descriptive error
• Tests cover under-limit success, over-limit rejection, and window reset

Notes

Be mindful of ledger storage costs per caller — document the storage footprint of the limiter state.