Use app favicon

[Wheezily]

Fixes #922.

The app shell was still loading the favicon from the old site logo at /_img/index/logobox.png. This points the page at the app favicon instead and adds src/favicon.ico to the Angular build assets so the file is emitted.

Validation:

• node -e "const fs=require('fs'); JSON.parse(fs.readFileSync('angular.json','utf8')); if(!fs.existsSync('src/favicon.ico')) process.exit(1); console.log('angular.json ok; favicon exists');"
• git diff --check

I did not run a full Angular build locally because dependencies are not installed in this checkout.

[Wheezily]

Added a fuller local validation pass:

• Installed dependencies in a Node 18 container with the Cypress binary download disabled.
• Fetched full git history so the changelog step can resolve its base commit.
• Ran npm run build; it passed with the existing Angular/CommonJS/Sass warnings.
• Re-ran git diff --check; it passes.