[codex] Update toolbar site branding

[DavidBabinec]

Summary

• Replace the committed app favicon with the uploaded database-style favicon logo.
• Restore the toolbar brand behavior to use the configured site favicon when one exists, otherwise show the site name as compact bold text matching the admin navigation.
• Remove the Untitled Site pre-hydration fallback and render the shared Skeleton while site identity is still loading.
• Keep the site name in the shared tooltip and remove native title tooltip usage.

Validation

• bun test
• bun run build
• bunx eslint src/admin/pages/site/toolbar/Toolbar.tsx src/admin/state/adminUi.ts src/admin/state/useSiteSummary.ts src/admin/layouts/AdminCanvasLayout/AdminCanvasLayout.tsx src/__tests__/toolbar/toolbarBrand.test.tsx src/__tests__/layout/editorLayoutPersistence.test.tsx src/__tests__/data/contentAdmin.test.tsx src/__tests__/toolbar/toolbar.test.ts src/__tests__/architecture/no-native-title-tooltips.test.ts --parser-options '{"tsconfigRootDir":"/Users/davidbabinec/Documents/Projekty/instatic"}'
• bunx react-doctor@latest --verbose --diff
• Browser smoke on disposable local stack: setup/login succeeded, toolbar brand rendered My Site with 11px/700/28px nav-matched styling and no Untitled Site text.