Add bounded machine funding contract role

[ameya-deshmukh]

Summary

• add a dedicated machine-operator role for exact sUSDC transfers
• cap each exact transfer and keep machine operators separate from super operators
• grant the configured operator during deployment and synchronize both frontend ABIs

Test plan

• sforge fmt --check
• sforge build
• sforge test
• bun run scripts/check-contract-abi.ts
• frontend and community-frontend typechecks and production builds

Stack

1 of 4. Split from #35. Merge this PR first; next is #38.

Fixes SEI-414 — https://linear.app/seismic-systems/issue/SEI-414/3-machine-funding-add-a-bounded-contract-operator-role

[linear-code]

SEI-414