fix: resolve #455 #296 #355 #352 in contracts and backend indexer

[umuewu]

Description

This PR bundles fixes for loan approval liquidity accounting, lending pool share pricing query exposure, and backend multi-contract event indexing so pool/portfolio views stay accurate.

Closes #455
Closes #296
Closes #355
Closes #352

Changes proposed

What were you told to do?

Implement and submit one PR that addresses four open issues: the loan-manager outstanding liquidity check, RemittanceNFT cooldown cleanup on burn, lending-pool share-accounting gaps, and backend event indexing across LoanManager/LendingPool/RemittanceNFT.

What did I do?

LoanManager liquidity commitment tracking

• Added DataKey::TotalOutstanding(token) tracking in contracts/loan_manager/src/lib.rs.
• Updated approve_loan() to enforce pool_balance - total_outstanding >= loan.amount before approval.
• Incremented outstanding on approval and decremented it on full repayment/default paths.
• Updated refinance logic to adjust outstanding deltas and apply liquidity checks against available uncommitted balance.
• Added regression test for back-to-back approvals that exceed pool capacity once prior approved loans are accounted for.

LendingPool/API surface and indexer coverage

• Added get_share_price(token) in contracts/lending_pool/src/lib.rs (scaled fixed-point quote for share valuation).
• Extended backend event-indexer webhook event support to include LendingPool and RemittanceNFT event types.
• Updated EventIndexer to accept multiple contracts (contractConfigs/contractIds) and fetch events across all configured contract IDs.
• Updated indexerManager to wire LOAN_MANAGER_CONTRACT_ID, LENDING_POOL_CONTRACT_ID, and REMITTANCE_NFT_CONTRACT_ID into one multi-contract indexer configuration.

RemittanceNFT burn cooldown issue

• Verified burn_internal() already removes DataKey::TransferCooldown(user) in current codebase, so no additional code change was required in this branch.

Check List (Check all the applicable boxes)

• My code follows the code style of this project.
• This PR does not contain plagiarized content.
• The title and description of the PR is clear and explains the approach.
• I am making a pull request against the main branch (left side).
• My commit messages styles matches our requested structure.
• My code additions will fail neither code linting checks nor unit test.
• I am only making changes to files I was requested to.

Screenshots / Testing Evidence

Per request, tests were not run in this task. Formatting applied to touched backend TypeScript files via Prettier. Rust formatter (cargo fmt) was unavailable in this shell environment.