[Quality] Add stateful invariant tests across lending lifecycle operations

[1nonlypiece]

Problem

Unit tests cover individual paths, but sequences of deposit, borrow, repay, withdraw, accrual, and liquidation can violate global invariants.

This issue requires a meaningful production implementation. Typo-only, documentation-only, formatting-only, dependency-only, or cosmetic changes do not satisfy the scope.

Objective

Build a bounded stateful/property test model for the lending workspace.

Scope

Define generated actors/assets, model balances and debt, shrinking, deterministic seeds, and CI runtime limits.

Acceptance criteria

• Generated sequences preserve debt, collateral, reserve, and authorization invariants.
• Invalid operations fail without partial mutation.
• Failures provide a reproducible minimized seed and sequence.
• The suite runs reliably in CI and complements existing targeted tests.
• Existing CI/CD checks remain green.
• The PR explains the design, tradeoffs, test evidence, and any remaining limitations.
• The PR references this issue with Closes #{issue-number} or Fixes #{issue-number}.

Implementation notes

Implement only the stated behavior; keep unrelated refactors out of the PR.

Non-goals

• Do not remove tests merely to make CI pass.
• Do not introduce secrets, private keys, credentials, or mainnet-only values.
• Do not change unrelated APIs, UI surfaces, contract behavior, or deployment configuration.

Contributor application

Before starting, comment with relevant experience, a 1–4 bullet implementation approach, and an estimate for opening the first draft PR. Wait for maintainer assignment before coding. Only the assigned contributor is eligible for reward consideration.

Submission requirements

• Use PR title format [#<issue-number>] <short summary>.
• Check off each completed acceptance criterion.
• Include focused automated tests for success, failure, authorization, and boundary behavior where applicable.
• Include the validation commands and results in the PR description.
• Address maintainer review feedback before merge.

GrantFox reward consideration is based on the original scope, implementation quality, tests, security review, CI/CD results, review feedback, and follow-up stability; completion or merge alone is not a guarantee.

[malaysiaonelove]

Hi maintain,I will love to work on this issue,I have an experience and I have already reviewed the issue please assigned me to it and I will give a good result.

[malaysiaonelove]

Hi maintain,I will love to work on this issue,I have an experience and I have already reviewed the issue please assigned me to it and I will give a good result.

[grantfox-oss]

🦊 GrantFox — @malaysiaonelove has been assigned to this issue!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #1904)
2. Your PR will be reviewed by the StellarLend maintainers

Good luck! Track your progress on GrantFox.