fix: use new server URL for ctx

[christinehc]

This updates the host URL for the CompTox API to the new server at https://comptox.epa.gov/ctx-api/

The following code has been tested to not work with the old server host and works now with the changes:

import ctxpy as ctx
CTX_API_KEY = "api-key-goes-here"
chem = ctx.Chemical(x_api_key=CTX_API_KEY)
chem.search(by="equals", word="290352-28-2")

Returns:

[{'dtxsid': 'DTXSID7047306',
  'dtxcid': 'DTXCID5027306',
  'casrn': '290352-28-2',
  'preferredName': 'CP-634384',
  'hasStructureImage': 1,
  'smiles': 'CC1=CC(NC(=O)C(O)=O)=CC(C)=C1OC1=CC=C(O)C2=C1CCC2',
  'isMarkush': False,
  'searchName': 'CAS-RN',
  'searchValue': '290352-28-2',
  'rank': 5}]

--
Changes:

• fix: Updated server URL in base.CTXConnection
• format: Applied formatting/linting using ruff and isort