feat(kzg): add KZG-based ingress proofs, blob extraction, and custody proof system DO NOT MERGE

[glottologist]

Describe the changes
THIS IS RESEARCH ONLY - DO NOT MERGE

Before: Ingress proofs used only SHA-256 hashes (V1). No blob support. No custody proof mechanism.
After: KZG commitment-based V2 ingress proofs, EIP-4844 blob extraction, and complete custody proof challenge-response loop.

What is KZG and why does this matter?

The problem: Irys miners store 256 KB data chunks and prove they received them via ingress proofs. The existing proof (V1) is a SHA-256 merkle root — it proves "I hashed all the chunks together," but there's no way to later challenge a miner about individual chunks without re-downloading everything.

The solution: KZG commitments. A KZG commitment is a 48-byte elliptic curve fingerprint of data that supports point evaluation — a verifier can pick any position and ask "what's the value here?", and the prover must answer with a short proof. Faking a valid answer requires breaking a hard cryptographic assumption (discrete log on BLS12-381). This uses the same cryptography and trusted setup as Ethereum's EIP-4844 blobs, via the c-kzg library already in our dependency tree through Reth.

What this PR adds

1. KZG ingress proofs (V2) — A new proof type where the data fingerprint is a KZG commitment instead of a merkle hash. Each 256 KB chunk is split into two 128 KB halves (matching the EIP-4844 blob size), each half is committed separately, then the two commitments are aggregated into one. Per-chunk commitments are stored in the database for later custody verification.

2. Custody proofs — A challenge-response protocol: when a block is confirmed on-chain, its VDF output seeds deterministic random challenges ("prove you still hold chunk N in your partition"). Miners compute KZG opening proofs on their stored data and gossip the results. Peers verify proofs against stored per-chunk commitments. Invalid proofs generate penalty shadow transactions. The full loop is wired: challenge issuance → proof generation → gossip → block inclusion → validation.

3. EIP-4844 blob extraction — A new service that pulls blob sidecars from the Reth blob store, converts each blob into an Irys native transaction with a V2 ingress proof, and feeds it into the mempool. After extraction, blob-derived data is indistinguishable from native data.

Detailed Primer on KZG Proofs

Related Issue(s)
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Checklist

• Tests have been added/updated for the changes.
• Documentation has been updated for the changes (if applicable).
• The code follows Rust's style guidelines.

Additional Context
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