feat: dividends, whitelist, governance sync, and key transfer

[brightcli-stack]

Fixes #817
Fixes #819
Fixes #820
Fixes #821

What changed

• Added GET /investor/:wallet/dividends endpoint with cursor pagination for dividend payout records
• Added POST /investor/:keyId/whitelist/add, POST /investor/:keyId/whitelist/remove, and GET /investor/:keyId/whitelist/addresses endpoints for whitelist management
• Added governance proposal sync job that auto-closes expired proposals
• Added POST /keys/:keyId/transfer endpoint with balance validation and atomic DB update
• Added Dividend and Whitelist Prisma models

Why

• Investors need to query their dividend payout history (Add an investor dividend receipts endpoint listing all dividend payouts received by a wallet across all keys #817)
• Creators need whitelist management for their key holders (Add a creator whitelist management endpoint to add and remove approved wallet addresses #819)
• Governance proposals need to be synced and auto-closed when expired (Add a governance proposal sync job that writes on-chain proposal and vote events to the database #820)
• Key holders need to transfer keys between wallets (Add a key transfer endpoint that records peer-to-peer transfers and updates holder balances in the database #821)

How to test

• Run prisma migrate dev to apply new schema
• Test dividend listing: GET /api/v1/investor/:wallet/dividends
• Test whitelist: POST /api/v1/investor/:keyId/whitelist/add with { "address": "..." }
• Test transfer: POST /api/v1/keys/:keyId/transfer with { "fromAddress": "...", "toAddress": "...", "quantity": 1 }
• Verify governance sync job runs via GOVERNANCE_SYNC_ENABLED=true env var

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