[Fix] DeFindex errors silently swallowed in orchestration.ts returning partial data as HTTP 200 #234

Description

In packages/stellar-sdk-helpers/src/orchestration.ts:58, the catch block around fetchDefindexPosition logs a warning and continues, returning only Blend positions to the caller. The caller (the API route) receives an HTTP 200 response with DeFindex balances silently omitted.

There is no partial-data signal in the response -- callers cannot distinguish a complete result from one where DeFindex fetching failed.

Steps to Reproduce

1. Set VAULT_CONTRACT_ID to a value that causes fetchDefindexPosition to throw (wrong contract ID, RPC timeout, etc.).
2. Call the positions API endpoint.
3. Observe HTTP 200 with Blend positions only -- no error, no indication DeFindex data is missing.

Expected Behavior

The caller receives a clear signal that the result is partial -- either a non-200 status, a typed partial-data flag in the response body, or a rethrown error.

Actual Behavior

All fetchDefindexPosition errors are caught and discarded. The caller gets a successful response containing only Blend data.

Environment

Possible Cause / Fix

Either rethrow the error (letting the API route return a 5xx), or add a partial: true flag to the response type and surface it to callers so they can handle it explicitly.