Implement protocol fee accounting on milestone release (protocol_fee_bps)

[mikewheeleer]

Description

The README and .kiro/specs/fee-accounting-tests describe a configurable protocol_fee_bps deducted from each release_milestone, with accumulated fees tracked in treasury, but contracts/escrow/src/lib.rs contains no fee logic — release_milestone credits the full milestone amount and DataKey::ProtocolFeeBps / DataKey::AccumulatedProtocolFees are declared yet unused. Implement fee calculation, net-amount accounting, and treasury accumulation.

Requirements and context

• Scoped to TalentTrust escrow Soroban contract (contracts/escrow).
• Add set_protocol_fee_bps(admin, bps) (admin-gated via require_admin) storing under DataKey::ProtocolFeeBps; clamp to a max of 1000 bps (10%) per the fee spec.
• In release_milestone, compute fee = milestone_amount * bps / 10_000 (round down), net = milestone_amount - fee, add fee to DataKey::AccumulatedProtocolFees, and credit net to the freelancer accounting.
• Invariant: fee + net == milestone_amount after rounding; accumulated fees never exceed total released; default bps == 0 pays the full amount.
• Must be secure, tested, and documented.

Suggested execution

• Fork the repo and create a branch:
  • git checkout -b feature/protocol-fee-accounting
• Implement changes:
  • contracts/escrow/src/protocol_fees.rs
  • Tests: contracts/escrow/src/test/protocol_fees.rs
  • Docs: docs/escrow/FUNDING_ACCOUNTING.md
  • Include rustdoc/NatSpec-style doc comments on public functions
  • Validate security assumptions (auth, overflow, fail-closed state machine, storage TTL, fee accounting)

Test and commit

• Run tests: cargo test
• Cover edge cases (unauthorized callers, double release/refund, expired approvals, fee rounding, paused state)
• Include test output and security notes in the PR

Example commit message

feat(escrow): add protocol_fee_bps deduction on release

Guidelines

• Minimum 95% test coverage on new/changed code
• Clear documentation
• Timeframe: 96 hours from assignment

[victor62-art]

@victor62-art has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

studied the task at hand and i can say i have a clear understanding
pls assign me so i can begin implementation

ℹ️ Repo Maintainers: To accept this application, review their application or assign @victor62-art to this issue.

[drips-wave]

Congratulations, @victor62-art! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

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