feat: add code autocomplete dropdown using CodeMirror show-hint

[Adityapradh]

🧠 What this PR does

This PR adds a code autocomplete dropdown in the Code Editor using CodeMirror’s official show-hint addon.

🔧 Implementation Details

• Installed and imported show-hint, anyword-hint addons.
• Configured autocomplete trigger on Ctrl + Space.
• Added extraKeys option to enable the dropdown.
• Verified UI and CodeMirror behavior.

✅ Related Issue

Closes #2567