Change Proof inner representation from Vec<u32> to Vec<u8>

[m-kus]

Summary

Changes the inner representation of the Proof type from Vec<u32> to Vec<u8> across RPC,
gateway, and P2P layers.

Rationale

The proof is now compressed before being attached to the transaction, making it an opaque byte blob
rather than a sequence of u32 values. This was a last-minute change on the gateway side.

Spec references:

• RPC spec (WIP): fix: deserialization description for proof starkware-libs/starknet-specs#377
• P2P spec:
  starknet-io/starknet-p2p-specs@411d992

Changes

• crates/common/src/lib.rs — Proof(Vec<u32>) → Proof(Vec<u8>); simplified serde to direct
  base64 encode/decode (no more u32 packing, no multiple-of-4 validation)
• crates/rpc/src/dto/primitives.rs — removed intermediate u32 → big-endian bytes conversion
  step in DTO serialization
• crates/p2p_proto/proto/transaction.proto — repeated uint32 proof → bytes proof in
  InvokeV3WithProof
• crates/p2p_proto/src/transaction.rs — proof: Vec<u32> → proof: Vec<u8>
• crates/rpc/fixtures/0.10.0/broadcasted_transactions.json — updated expected base64 value

Notes

• RPC wire format is still a base64 string — no change for clients sending raw byte payloads
• P2P wire format is a breaking change (repeated uint32 → bytes)
• The proof field remains transient: accepted from clients, forwarded to the sequencer, propagated
  via mempool/consensus P2P, but never stored in the DB or included in the transaction hash (only
  proof_facts are)

[CHr15F0x]

LGTM mod the changelog.

[CHr15F0x]

👍

[kkovaacs]

LGTM