Add get_invoice_funding_progress view function

[Kingsman-99]

Description

There is no single entry point that returns the funding progress of an invoice expressed in basis points (funded * 10_000 / total). External dashboards and integration tests must compute this themselves from raw funded and amounts, duplicating logic that belongs in the contract.

Acceptance Criteria

• New read-only function get_invoice_funding_progress(invoice_id: u64) -> u32 added to the contract trait
• Returns funded * 10_000 / total clamped to [0, 10_000]
• Returns 0 when total == 0
• Returns ContractError::InvoiceNotFound for unknown IDs
• At least one unit test covers the happy path and the fully-funded case
• cargo test passes

Context

• Target file: contracts/split/src/lib.rs

[Oluoma123]

@Oluoma123 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Good day I am a full stack developer with Over 6 years of experience and I have good practical knowledge on this kindle assign this to me.

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[Maki-Zeninn]

@Maki-Zeninn has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

please assign me this, i've scoped this issue out and i'm certain i can resolve it

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Congratulations, @Maki-Zeninn! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Third Campaign campaign!

@Maki-Zeninn's PR #710 was approved and merged by @Kingsman-99.

🏆 @Maki-Zeninn: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (780 total points). Track your full progress on GrantFox.

👏 Great work, @Maki-Zeninn! Keep contributing to Stellar-split.

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This issue has been completed by @Maki-Zeninn as part of the Stellar Wave Program's 8th Wave 🥳

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