Protect against donation-based price manipulation attacks

[Smartdevs17]

Description

Attackers can manipulate pool prices via direct token donations. Implement donation detection and mitigation.

Acceptance Criteria

• Donation detection via balance vs accounting delta
• Virtual share price to dilute donation impact
• Minimum deposit amount to prevent dust attacks
• Donation-based manipulation test scenarios
• Integration with liquidation pricing
• Documentation of donation attack surface

Technical Scope

• stellar-lend/contracts/lending/src/
• stellar-lend/contracts/hello-world/src/
• Edge: legitimate balance changes (airdrops), donation detection false positives

[TUPM96]

Implemented this in PR #402: #402

Coverage added:

• balance-vs-accounting donation detection
• quarantined unaccounted balances and virtual share price that excludes donations
• configurable dust/min-deposit and donation tolerance controls
• liquidation blocked while debt/collateral asset has an active donation alert
• tests for donation manipulation, dust prevention, and liquidation alert handling
• documentation of the donation attack surface

[Flamki]

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

i would like to work on this

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

[OlaBakare]

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

Hi, I'd love to work on this issue. I can handle this issue.
Thank you.

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

[Ugasutun]

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

Hi, I’d like to work on issue #389. I understand the donation-based manipulation risk and can implement the required protections, tests, and documentation, including handling edge cases like airdrops and false positives.

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

[Adeyemi-cmd]

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

I’d be a good fit for this task because I can contribute to building secure donation-attack mitigation systems, improve pricing integrity, handle edge cases like false-positive balance changes, and ensure the protocol is backed by solid testing and reliable contract behavior.

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