Implement Error Handling for HTTP API

[farhoud]

Title: Implement Error Handling for Index and Search Endpoints

Description:
Handle common errors for the HTTP API endpoints to ensure robust and user-friendly responses.

Acceptance Criteria:

• Return a 400 Bad Request error for missing required fields.
• Return a 404 Not Found error for no matching search results.
• Return a 500 Internal Server Error for unexpected server errors.

Response Examples:

• 400 Bad Request:

  {
    "status": "error",
    "message": "Missing required fields."
  }

• 404 Not Found:

  {
    "status": "error",
    "message": "No matching results found."
  }

• 500 Internal Server Error:

  {
    "status": "error",
    "message": "An unexpected error occurred. Please try again later."
  }

Tasks:

• Implement error handling for the /index endpoint.
• Implement error handling for the /search endpoint.