feat: import and map native browser bookmarks

[WangEn]

What changed

• move Chromium bookmarks access from required install-time permission to optional runtime permission
• bump Dockmark Extension to 0.2.0
• expose native bookmark capability + granted-permission state in the Browser Bridge handshake
• read the browser bookmark tree through the trusted Web/Extension bridge, preserving folder paths
• add reviewed native bookmark import to the Transfer page
• de-duplicate same-URL browser bookmarks into one Dockmark bookmark
• map native bookmark IDs to Dockmark bookmark IDs in extension-local storage only
• automatically prune mappings when a native bookmark is removed or its URL changes
• allow already-existing Dockmark URLs to be linked without creating duplicates
• keep native bookmark import read-only: no browser bookmark create/update/move/delete operations
• update Chromium smoke coverage for extension 0.2.0 and optional bookmark permission semantics

Mapping boundary

browserBookmarkId ↔ dockmarkBookmarkId lives only in browser.storage.local; browser-internal IDs are not written to D1. This PR intentionally does not implement two-way sync or destructive native bookmark mutation.