starknet_transaction_prover: add request body size limit tests

[avi-starkware]

Adds integration tests for the JSON-RPC server's max_request_body_size enforcement — previously untested at the prover-server level:

• test_default_limit_accepts_5000_felt_calldata — a starknet_proveTransaction request carrying 5,000 full-width (Felt::MAX) calldata felts (~350 KiB body, the largest JSON encoding such calldata can produce) is accepted under the production-default 5 MiB limit. DEFAULT_MAX_REQUEST_BODY_SIZE is made pub(crate) so the test tracks the real default.
• test_body_size_limit_boundary — the limit is inclusive: a body of exactly the configured size is served; one byte over is rejected with HTTP 413.

🤖 Generated with Claude Code

[cursor]

PR Summary

Low Risk
Test-only change plus making a default constant visible to the crate; no production server logic changes.

Overview
Adds HTTP integration tests for jsonrpsee’s max_request_body_size on the transaction prover server, without changing runtime behavior.

DEFAULT_MAX_REQUEST_BODY_SIZE (5 MiB) is now pub(crate) so tests can assert against the same default the service uses. A new request_body_size_test module spins up a mock HTTP server via start_server and posts JSON-RPC bodies.

One test checks that a large starknet_proveTransaction payload (5,000 max-width calldata felts, ~350 KiB) succeeds under the default limit. Another uses rstest to confirm the limit is inclusive: a body padded to exactly the configured size returns 200, and one extra byte returns 413 Payload Too Large.

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[reviewable-StarkWare]

This change is 

[avi-starkware]

• starknet_transaction_prover: add deployment smoke script and guide #14052
• starknet_transaction_prover: add manual testing guide #14404
• starknet_transaction_prover: drop stale dead_code allow on RpcVirtualBlockExecutor #14740
• starknet_transaction_prover: extract shared server test utils #14739
• starknet_transaction_prover: make RPC error spec test exhaustive via enum #14051
• starknet_transaction_prover: add TLS integration tests #14050
• starknet_transaction_prover: add ServiceConfig validation tests #14049
• starknet_transaction_prover: add CORS validation unit tests #14048
• starknet_transaction_prover: add prover input validation unit tests #14047
• starknet_transaction_prover: add committer utils unit tests #14046
• starknet_transaction_prover: add request body size limit tests #14403 👈 (View in Graphite)
• main-v0.14.3

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[Yoni-Starkware]

@Yoni-Starkware reviewed 3 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on avi-starkware).