Fix: Health check now verifies server response

[echobt]

Summary

This change ensures the health check function properly validates the server response instead of only checking if a TCP connection and write operation succeeded.

Problem

The health() function in src/server/client.rs only verified that it could establish a TCP connection and write an HTTP request. It immediately returned true after a successful write without reading or validating the server response. This means a hung or malfunctioning server that accepts connections but never responds would still be reported as healthy, potentially causing cascading failures in systems relying on accurate health status.

Solution

Modified the health() function to:

1. Send the HTTP GET /health request
2. Read the HTTP status line from the response
3. Parse the HTTP status code and verify it is in the 2xx success range
4. Only return true if the server responds with a successful status code

This ensures that the health check accurately reflects whether the server is actually processing requests and responding correctly.

Testing

The fix follows the same HTTP response reading pattern used by the search() and embed_batch() methods in the same file, which have been working correctly. The health check will now return false if:

• Connection fails
• Write fails
• Flush fails
• Reading the response fails
• The HTTP status code is not in the 200-299 range

Related Issue

Fixes PlatformNetwork/bounty-challenge#19