Fix console errors

[jhaals]

• Updated Content-Security-Policy in netlify.toml to include img-src directive.
• Modified SecurityHeadersHandler in server.go to support img-src.
• Replaced inline theme initialization script in index.html with an external theme-init.js file for better maintainability.
• Added theme-init.js to handle theme mode detection and application.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.21%. Comparing base (df15cae) to head (7903854).
⚠️ Report is 17 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3006      +/-   ##
==========================================
+ Coverage   82.18%   82.21%   +0.02%     
==========================================
  Files           8        8              
  Lines         741      742       +1     
==========================================
+ Hits          609      610       +1     
  Misses         98       98              
  Partials       34       34              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[jhaals]

fixes #3000