Add edit bookmark, offline cache, and unread filter

- Edit bookmark: full PATCH via swipe action or long-press context menu;
  EditBookmarkView covers URL, title, description, tags, and unread toggle
- Offline cache: bookmarks persisted to ApplicationSupport JSON and shown
  instantly on launch; cache is per-server, skipped when unread filter is on
- Unread filter: toolbar toggle sends ?unread=true to the API; title updates
  to "Unread"; no stale-cache flash when toggling
- Extract normalizedURL and parsedTags into String+Helpers, removing three
  copies of URL normalization and two of tag parsing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Marks/Services/LinkdingAPI.swift

@@ -57,12 +57,13 @@ actor LinkdingAPI {
         return req
     }
 
-    func fetchBookmarks(search: String = "", offset: Int = 0, limit: Int = 50) async throws -> BookmarkResponse {
+    func fetchBookmarks(search: String = "", offset: Int = 0, limit: Int = 50, unread: Bool = false) async throws -> BookmarkResponse {
         var items: [URLQueryItem] = [
             .init(name: "limit", value: "\(limit)"),
             .init(name: "offset", value: "\(offset)")
         ]
         if !search.isEmpty { items.append(.init(name: "q", value: search)) }
+        if unread { items.append(.init(name: "unread", value: "true")) }
         let url = try makeUrl(path: "/api/bookmarks/", queryItems: items)
         let (data, response) = try await session.data(for: authorizedRequest(url: url))
         guard (response as? HTTPURLResponse)?.statusCode == 200 else {
@@ -87,8 +88,8 @@ actor LinkdingAPI {
         return try decoder.decode(Bookmark.self, from: data)
     }
 
-    func updateBookmark(id: Int, tagNames: [String]) async throws -> Bookmark {
-        let body = try JSONEncoder().encode(["tag_names": tagNames])
+    func updateBookmark(id: Int, update: BookmarkUpdate) async throws -> Bookmark {
+        let body = try JSONEncoder().encode(update)
         let url = try makeUrl(path: "/api/bookmarks/\(id)/")
         let (data, response) = try await session.data(for: authorizedRequest(url: url, method: "PATCH", body: body))
         guard (response as? HTTPURLResponse)?.statusCode == 200 else {