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/Views/BookmarksView.swift

@@ -8,6 +8,7 @@ struct BookmarksView: View {
     @State private var showSettings = false
     @State private var showCollections = false
     @State private var showAddBookmark = false
+    @State private var editingBookmark: Bookmark?
 
     var body: some View {
         NavigationStack {
@@ -34,6 +35,35 @@ struct BookmarksView: View {
                                 Label("Archive", systemImage: "archivebox")
                             }
                             .tint(.orange)
+                            Button {
+                                editingBookmark = bookmark
+                            } label: {
+                                Label("Edit", systemImage: "pencil")
+                            }
+                            .tint(.blue)
+                        }
+                        .contextMenu {
+                            Button {
+                                editingBookmark = bookmark
+                            } label: {
+                                Label("Edit", systemImage: "pencil")
+                            }
+                            Button {
+                                if let url = URL(string: bookmark.url) { openURL(url) }
+                            } label: {
+                                Label("Open", systemImage: "safari")
+                            }
+                            Divider()
+                            Button {
+                                Task { await viewModel.archive(bookmark) }
+                            } label: {
+                                Label("Archive", systemImage: "archivebox")
+                            }
+                            Button(role: .destructive) {
+                                Task { await viewModel.delete(bookmark) }
+                            } label: {
+                                Label("Delete", systemImage: "trash")
+                            }
                         }
                 }
 
@@ -43,7 +73,7 @@ struct BookmarksView: View {
                 }
             }
             .listStyle(.plain)
-            .navigationTitle("Bookmarks")
+            .navigationTitle(viewModel.unreadFilter ? "Unread" : "Bookmarks")
             .navigationBarTitleDisplayMode(.large)
             .toolbar {
                 ToolbarItem(placement: .topBarLeading) {
@@ -70,6 +100,13 @@ struct BookmarksView: View {
                         Button { showAddBookmark = true } label: {
                             Image(systemName: "plus")
                         }
+                        Button {
+                            Task { await viewModel.toggleUnreadFilter() }
+                        } label: {
+                            Image(systemName: viewModel.unreadFilter
+                                  ? "line.3.horizontal.decrease.circle.fill"
+                                  : "line.3.horizontal.decrease.circle")
+                        }
                         Button { showSettings = true } label: {
                             Image(systemName: "gearshape")
                         }
@@ -99,6 +136,9 @@ struct BookmarksView: View {
         .sheet(isPresented: $showAddBookmark) {
             AddBookmarkView(viewModel: viewModel)
         }
+        .sheet(item: $editingBookmark) { bookmark in
+            EditBookmarkView(viewModel: viewModel, bookmark: bookmark)
+        }
         .refreshable {
             await viewModel.load()
         }