feat(error-trace): add execute proof trace field

[fakedev9999]

Summary

• Adds optional ExecuteProofRequestBody.error_trace = 11 to the network wire type.
• Keeps it wire-aligned with network-services j/vapp, which already receives, sanitizes, and stores this field (requests.error_trace).
• Enables the follow-up sp1-cluster-private MainnetExecutor wiring to send structured traces on execute_proof.

Scope

• Wire contract only: proto field + regenerated Rust types.
• No producer wiring in this PR (sp1-cluster-private unchanged).
• No network-services / infra / release changes.
• Additive and backward-compatible: optional field, next free tag (11); old producers omitting it decode as None, old consumers ignore it.
• Does not capture guest panic payload/location (separate SP1 stderr-capture work).

Validation

• cargo build -p spn-network-types --release (regenerates src/types.rs via build.rs)
• cargo test -p spn-network-types error_trace --lib → 52 passed
• cargo fmt -p spn-network-types -- --check → clean
• git diff --check → clean
• Diff limited to proto/types.proto (+ field) and crates/types/network/src/types.rs (regenerated): #[prost(bytes = "vec", optional, tag = "11")] error_trace.