Add SDK `joinFundQueue` and `resolveFundQueue` methods

[Levi-Ojukwu]

Description:

The LP priority queue allows LPs to compete for funding rights based on reputation. The SDK needs methods for:

1. joinFundQueue(lp, invoiceId) — register LP's intent, snapshot their score
2. resolveFundQueue(invoiceId) — select the highest-score LP as approved funder

Why it matters: LP priority queuing is a key feature for fair invoice allocation.

Acceptance Criteria:

• Create both methods with proper validation
• Handle AlreadyInQueue and NotApprovedFunder errors
• Add tests for queue ordering logic

Relevant Files: contracts/invoice_liquidity/src/lib.rs:939-1038, sdk/src/index.ts

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[michaelvic123]

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[circleboyslimited]

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