End-to-End Integration Test for Full Invoice Lifecycle

[Kingsman-99]

Description

There is no single test that exercises the complete invoice lifecycle — creation, contribution, full funding, release, and archival — using realistic token balances and multiple addresses. A comprehensive end-to-end test should serve as a regression suite for all major contract interactions.

Technical Context

Create tests/e2e_lifecycle.rs using soroban_sdk::testutils and the shared helpers from tests/helpers.rs. Simulate three contributors funding an invoice split three ways, verify token balances before and after payout, check event emissions, confirm archival, and assert get_invoice returns InvoiceNotFound while get_archived_invoice succeeds. Use MockAuth for all auth steps.

Acceptance Criteria

• Test covers create → contribute (×3) → fully funded → release → archived flow
• Token balances for all parties are asserted before and after each major step
• All expected events (InvoiceCreated, ContributionMade, InvoiceReleased, etc.) are captured and checked
• Test fails if the invoice is not found via get_archived_invoice after release
• Fee recipient balance is asserted to have received the correct fee amount
• All CI checks (cargo build --target wasm32-unknown-unknown, cargo test, cargo clippy) pass and the branch has no merge conflicts

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[pleasureiliya69-ops]

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