feat: combined activity endpoint GET /transfers/address/:address

[Miracle656]

Problem

The wallet (and any client) currently needs to make two separate requests — /transfers/incoming/:address and /transfers/outgoing/:address — then merge and sort the results client-side. This doubles the request count and pushes sorting logic onto every consumer.

Proposed solution

Add a new endpoint:

GET /transfers/address/:address

Returns both incoming and outgoing transfers in a single response, sorted by ledger descending.

Response shape:

{
  "total": 42,
  "limit": 50,
  "offset": 0,
  "transfers": [
    {
      "id": 1,
      "eventType": "transfer",
      "direction": "incoming",
      "fromAddress": "G...",
      "toAddress": "C...",
      "amount": "100000000",
      "ledger": 1794688,
      "ledgerClosedAt": "2025-01-01T00:00:00Z",
      "txHash": "abc123",
      "contractId": "C..."
    }
  ]
}

A direction field ("incoming" | "outgoing") should be added to each record so clients can still distinguish direction.

Supports all existing query params: contractId, fromLedger, toLedger, limit, offset.

Acceptance criteria

• GET /transfers/address/:address returns merged results sorted by ledger desc
• Each record includes a direction field
• Existing /incoming and /outgoing endpoints unchanged
• Pagination works correctly across the merged set