fix: set gas price explicitly when submitting votes

[suntzu93]

Problem

Both deny_many implementations in availability-oracle/src/contract.rs submitted votes without setting any fee field:

tx.gas(increased_estimate).send().await?.await?;

With no fee fields set, ethers fills in the EIP-1559 values using eip1559_default_estimator. That estimator does not consult the chain when the base fee is low — it returns a flat constant:

// ethers-core-2.0.14/src/utils/mod.rs:88
pub const EIP1559_FEE_ESTIMATION_DEFAULT_PRIORITY_FEE: u64 = 3_000_000_000; // 3 gwei

It uses that constant verbatim whenever the base fee is below EIP1559_FEE_ESTIMATION_PRIORITY_FEE_TRIGGER (100 gwei). On Arbitrum the base fee is ~0.02 gwei, so this branch is taken every time and every vote offers a 3 gwei tip.

That was harmless while Arbitrum discarded priority fees. Since 2026-09-23 the tip is actually charged, and the effective gas price on oracle votes jumped from 0.0200 to 3.0200 gwei — a 151x increase. Measured on the mainnet oracle (index 4): cost per vote went from ~$0.0014 to ~$0.28, and a single voteMany reached $7.98.

data_edge.rs was never affected, because it already sets its gas price explicitly.

Fix

Set the gas price explicitly at both vote call sites, mirroring data_edge.rs, so ethers never reaches for its default estimator. The 20% buffer matches what data_edge.rs uses.

Verification

cargo check clean. Deployed to the mainnet oracle and confirmed on chain:

	Before	After
Priority fee	3.000 gwei	0.024 gwei
Effective gas price	3.0200 gwei	0.0240 gwei
Gas used	476,337	541,172
Fee	~$4.03	~$0.035

The transaction still goes out as EIP-1559, but with the priority fee set to the buffered base fee rather than the estimator's 3 gwei.