Support per-page navbar configuration in multipage apps (#11865)
* changes
* add changeset
* changes
* Implement per-page navbar configuration support
- Add page_navbar_configs to store navbar settings per page
- Update Embed.svelte to use page-specific navbar configurations
- Remove global navbar fallback and unused navbar_config store
- Add navbar.svx documentation files for all template versions
- Update multipage apps guide with per-page navbar examples
* chagnes
* changes
* revert
* changes
* add changeset
* clean
* chanages
* add unit test
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