refactor: remove majority rule and switch to single Espresso client

[miguelCyclone]

Description
This PR replaces the previous NewMultipleNodesClient() usage with a single-client configuration based on NewClient()

Changes:

• Removed majority-rule logic from cli.go and service,go
• Updated to initialise a NewClient() instance from the first QueryServiceURLs entry.

Reasoning:

• Current integration uses a duplicated URL value for QueryServiceURLs.
• The Asana ticket (“Remove majority rule”) requests deprecation of the multi-node client.
• NewClient() matches the desired simplified behaviour while keeping compatibility with the EspressoClient interface.

Tests:

• just smoke-tests → passed
• just fast-tests→ passed
• Code builds successfully inside Nix shell
• No changes to CLI/API surface

Let me know if you want any adjustments or a different approach.

---

• To see the specific tasks where the Asana app for GitHub is being used, see below:
  • https://app.asana.com/0/0/1211924412675745

[CLAassistant]

All committers have signed the CLA.