feat: add isolated ERC20 USDC machine faucet

[ameya-deshmukh]

Summary

• deploy a standard 6-decimal testnet USDC and independent ERC20 machine faucet
• add opt-in internal ERC20 funding and readiness routes with dedicated signer, nonce queue, limits, and deployment identity
• keep the existing sUSDC contracts, routes, signer queue, frontends, nginx, and Supervisor behavior unchanged
• add failure-atomic deployment/preflight tooling and reserve-owned recovery

Fixes SEI-434 — https://linear.app/seismic-systems/issue/SEI-434/2-add-isolated-erc20-usdc-machine-faucet

Test plan

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace --locked
• cargo build --release --locked --workspace
• frozen install, typecheck, and build for both frontends
• sforge fmt --check, sforge build, and sforge test
• contract ABI check and Bash syntax check

[linear-code]

SEI-434