fix(txpool): reload queued senders on USDC storage changes

[Kewe63]

Summary

Closes #381

Fixes queued transaction reloads when a block mutates a sender's USDC predeploy balance. Previously, txpool maintenance only marked senders dirty when their native account state changed, so USDC-only balance slot updates did not cause queued transactions to be re-evaluated.

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Changes

• crates/transaction-pool/src/maintain.rs — add a hook extension point for queued senders affected by off-account state updates and invoke it after commit/reorg updates.
• crates/seismic/txpool/src/maintain.rs — detect changed USDC balance storage slots and mark matching queued senders dirty.
• crates/seismic/txpool/src/maintain.rs — add regression tests for filtering affected queued senders and unioning old/new state changes across reorgs.

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How to Test

cargo +nightly fmt --all --check
cargo +1.88.0 test -p reth-seismic-txpool
cargo +1.88.0 check -p reth-transaction-pool -p reth-seismic-txpool
cargo +1.88.0 clippy -p reth-seismic-txpool --lib --no-deps -- -D warnings -W clippy::unwrap_used -W clippy::expect_used -W clippy::indexing_slicing -W clippy::panic -W clippy::unreachable -W clippy::todo

Results:

• Formatting passed
• reth-seismic-txpool tests passed: 33 passed
• Targeted check passed
• Targeted Seismic txpool clippy passed

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Compatibility

No consensus, state format, wire protocol, or API compatibility impact.

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Checklist

• Tests pass — 33/33
• Formatting and clippy clean
• Follows Conventional Commits
• Changes scoped to this fix only

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Risk & Impact

Low-to-medium. The change affects txpool maintenance only and limits reloads to queued senders whose USDC balance storage slot changed. No consensus, state format, wire protocol, or API compatibility impact.

Type: 🐛 Bug fix
Closes: #381