refactor(ui): defer specialized frontend chunks

[alexk-dev]

Summary

This PR optimizes dashboard loading by keeping specialized frontend code out of the initial preload path.

• Splits CodeMirror, IDE tree, markdown, and charts dependencies into targeted Vite chunks instead of the generic startup vendor bundle.
• Lazy-loads the IDE code editor only when an editable file is opened, while warming the IDE/editor/analytics chunks during idle time after the authenticated dashboard shell paints.
• Loads CodeMirror language support by file extension instead of bundling the full language registry into the editor entry.
• Moves IDE-specific SCSS out of the main dashboard CSS and removes the unused @uiw/codemirror-extensions-langs dependency in favor of explicit CodeMirror language packages.

The production build now keeps the initial vendor chunk around 113 KB gzip, down from about 748 KB gzip in the baseline build. The editor core is deferred to about 139 KB gzip, and individual language parsers are loaded on demand.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud