[FE-48] Build insurance management UI — attach insurance policies to assets on-chain

[yusuftomilola]

Overview

Insurance details for assets can be stored on the Stellar blockchain for immutable record-keeping. This UI allows attaching an insurance policy to an asset and viewing the policy details. Depends on BE-64.

Context

• Add an "Insurance" section to the asset detail page (Overview tab or sub-tab)
• API endpoints (from BE-64): POST /stellar/assets/:id/insurance, GET /stellar/assets/:id/insurance
• Off-chain insurance records (without blockchain) are a future consideration

Acceptance Criteria

• Show current insurance status on the asset detail page: "No Insurance Recorded" or a policy summary card
• "Add Insurance" button opens a form: insurer name, policy number, coverage amount, premium (annual), start date, end date
• On submit: records to blockchain, shows confirmation with tx hash
• Policy card shows: insurer, policy number, coverage amount, premium, dates, status chip (ACTIVE / EXPIRING / EXPIRED based on end date), transaction hash
• Expiring policies (within 30 days) show a warning banner: "Policy expires in X days. Renew soon."