feat: e2e tests + framework

[kmchicoine]

• New e2e test crate: Adds end-to-end tests for the TIPS ingress RPC service, validating transaction and bundle submission flows against a running server
• Testing infrastructure: Includes JSON-RPC client, transaction signing fixtures, and helper utilities for creating test bundles and signers
• Mock provider: simulates blockchain state with high balances, enabling tests without real Ethereum node dependencies
• Test coverage: Tests empty/invalid input handling, single transactions, multi-transaction bundles, and bundle replacement with UUIDs
• Test gating: Tests that require the kafka queue are gated behind KAFKA_QUEUE_TESTS environment variable; set KAFKA_QUEUE_TESTS=1 to run these tests

[wlawt]

just curious, any reason for TxLegacy over TxEip1559?

[kmchicoine]

Great question, primarily because it had fewer arguments and was easier to work with initially. I'm about to push a change to fix the broken tests, so I can swap over to TxEip1559 (or if we want multiple types of transaction builders, happy to keep the TxLegacy and add TxEip1559 and subsequent tests)

[wlawt]

sounds good! i think we can leave txlegacy for now and then if we actually need txeip1559 later we can just swap it out in a follow up