feat: add Rosen Bridge FIRO ↔ rsFIRO swaps

[reubenyap]

Adds Rosen Bridge to the existing Swap flow for native FIRO ↔ rsFIRO on Ethereum mainnet. Users can create, fund, refresh, and resume swaps through the existing mobile/desktop confirmation screens and trade history.

Includes the rsFIRO and Campfire commits from #1444. Campfire can add FIRO, ETH, rsFIRO, USDC, and USDT wallets. The bridge and Add wallet share one rsFIRO contract definition.

Implementation

• Reuses Exchange, trade persistence, wallet signing/broadcast, FIRO coin selection, and ERC-20 transaction history. Uses existing coinlib address/hex helpers and web3dart ABI encoding.
• FIRO funding uses transparent funds with the required OP_RETURN; rsFIRO funding appends Rosen metadata to the ERC-20 transfer and pays gas in ETH. Signed transaction contents, mainnet, balances, fees, and nonce are checked before broadcast.
• Changed bridge fees require a refreshed quote and another confirmation. Concurrent funding and stale trade updates cannot erase a recorded deposit.
• Desktop wallet selection retains the selected wallet ID. Token registration preserves existing contract records.
• Keeps the existing flutter test --coverage workflow and prebuild configuration stubs. Fee regressions use normal test discovery. No new dependencies or workflows.

Protocol configuration and pinned upstream references are documented in docs/rosen_bridge.md.

Validation

• Passed 16 focused Flutter tests on macOS using the configured application dependencies: fee boundaries, protocol metadata, signed FIRO and ERC-20 transactions, Hive trade refresh/persistence, and Campfire token filtering.
• Targeted analysis found no compile errors; existing warnings/lints remain.
• Dart 3.12.2 formatting and git diff --check pass.

The full GitHub CI run must still pass. This remains a draft until the application flows and live transfers in both directions are validated; no funds were sent during testing.