/setup/setup-sync-info: Use better data types for response

Currently, all the `/setup/setup-sync-info` call sends are strings.

As a developer, I would like to have the numbers / booleans in there sent instead of strings, so I don't have to convert the strings and can make sure that just numbers / booleans are sent.

cc @rootzoll

```json
{
"initialsync": "running",
"btc_default": "bitcoin",
"btc_default_ready": "1",
"btc_default_sync_percentage": "100.00",
"btc_default_peers": "24",
"system_count_start_blockchain": "1",
"ln_default": "lnd",
"ln_default_ready": "1",
"ln_default_locked": "0",
"system_count_start_lightning": "1",
}
```

Start at the `/setup/setup-sync-info` API endpoint and inspect how its JSON response is assembled. Ensure numeric and boolean values are returned with those JSON types rather than as strings, while existing string values remain strings. Verify the response against the example fields and add or run the endpoint's existing tests if available.

Written by the indexing model from the issue text.