[Contract] Build Insurance Claims Management

[yusuftomilola]

Claims lifecycle management against active insurance policies.

Requirements

InsuranceClaim struct: claim_id: BytesN<32>, policy_id: BytesN<32>, asset_id: BytesN<32>, claimant: Address, claim_type: ClaimType (enum: Damage, Theft, Loss, Liability), amount: i128, status: ClaimStatus (Submitted, UnderReview, Approved, Rejected, Disputed, Paid), filed_at: u64, approved_amount: i128

Functions:

• file_insurance_claim(...) — claimant authenticates; policy must be Active; stores claim; indexes by asset ID
• mark_insurance_claim_under_review(env, claim_id, insurer) — insurer moves Submitted → UnderReview
• approve_insurance_claim(env, claim_id, insurer, approved_amount) — sets Approved, records amount
• reject_insurance_claim(env, claim_id, insurer) — insurer rejects Submitted or UnderReview
• dispute_insurance_claim(env, claim_id, claimant) — claimant disputes a Rejected claim
• pay_insurance_claim(env, claim_id, insurer) — marks Approved claim as Paid
• get_insurance_claim, get_asset_insurance_claims

Acceptance Criteria

• Claim can only be filed against an Active policy
• Status transitions enforced (e.g. cannot approve a Paid claim)
• approved_amount cannot exceed coverage_amount