feat: add full-text bookmark search

feat: add full-text bookmark search Adds the missing search capability on top of the existing browser: - KarakeepAPI:searchBookmarks() wrapping GET /bookmarks/search - SearchView rendering results through the shared transformBookmark path, so results are downloadable exactly like browsed bookmarks - Search entry in the browser root view, backed by an InputDialog - Empty-result state instead of a blank list Query params and enums verified against the Karakeep OpenAPI spec (searchMode: fts|semantic|hybrid, sortOrder: asc|desc|relevance).