API breaking changes without updating version number in routes

Since the DeSo rebrand, several fields on API responses have changed, e.g. a field on `get-exchange-rate` has gone from `SatoshisPerBitcloutExchangeRate` to `SatoshisPerDeSoExchangeRate`. The same is true for many fields across many responses that referenced the word "Bitclout".

This in itself is fine, but the routes are still set up as `/api/v0/:endpoint`, meaning it's not possible to deploy the latest version of the core/backend code without breaking any apps using the node.

The routes should make proper use of the version number, maintain `/v0` using the Bitclout field names, and use `v1` for the renamed DeSo fields.

Start by locating the HTTP route definitions for endpoints such as get-exchange-rate and identifying how response fields are assigned to the current /api/v0 routes. The work is done when /v0 preserves Bitclout field names and /v1 serves the renamed DeSo fields without breaking existing clients.

Written by the indexing model from the issue text.