feat: add Fireworks/Codestral 25.01 support for code completion

What does this merge request do and why?

Adds Codestral 2501 support on Fireworks to the AIGW

How to set up and validate locally

Update ENV file from example.env as the format for Fireworks related keys have changed

Fireworks API key can be found in the Engineering 1Password vault under Fireworks development key

curl -X "POST" "http://gdk.test:5052/v2/code/completions" \
     -H 'Content-Type: application/json; charset=utf-8' \
     -d $'{
  "current_file": {
    "content_below_cursor": "pageSource = document.querySelector(\'#hidden-page-source\').href\\n}, false);",
    "file_name": "main.go",
    "language_identifier": "go",
    "content_above_cursor": "document.addEventListener(\'DOMContentLoaded\', function() {\\n  webIDE = document.querySelector("
  },
  "model_provider": "fireworks_ai",
  "model_name": "codestral-2501",
  "prompt_version": 1
}'

Merge request checklist

• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.

Closes #832