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/BookmarkRow.swift

@@ -7,6 +7,14 @@ struct BookmarkRow: View {
         VStack(alignment: .leading, spacing: 6) {
             HStack(alignment: .top, spacing: 11) {
                 FaviconView(url: bookmark.faviconUrl)
+                    .overlay(alignment: .topLeading) {
+                        if bookmark.unread {
+                            Circle()
+                                .fill(.blue)
+                                .frame(width: 8, height: 8)
+                                .offset(x: -3, y: -3)
+                        }
+                    }
                     .padding(.top, 1)
 
                 VStack(alignment: .leading, spacing: 4) {