feat(share): dup-aware interactive save card with AI tag suggestions

Replace the fire-and-forget share toast with an interactive SwiftUI card.
On open it checks linkding's /api/bookmarks/check/ so an already-saved URL
routes to an Update (no more silent duplicates) and a new URL shows a save
form with title, tags, notes, and a read-later toggle.

Tag suggestions are hybrid: fetch the user's existing tag vocabulary
(/api/tags/) and AI tag ideas (/v1/marks/enrich via anonymous device auth),
auto-fill known-vocabulary matches into the field and surface net-new ideas
as tappable chips. Best-effort and non-blocking — failures never block save.

Also:
- Refresh bookmarks when the app returns to the foreground (scenePhase).
- Render bookmark dates as a static relative label instead of the live
  ticking RelativeDateTime timer.
- Share LinkdingAPI/Bookmark/ServerConfig/MarksAuth into the ShareExtension
  target via project.yml (durable across xcodegen regen) and regenerate.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Marks/Models/Bookmark.swift

@@ -61,6 +61,24 @@ struct BookmarkResponse: Codable, Sendable {
     let results: [Bookmark]
 }
 
+/// Response of linkding's `GET /api/bookmarks/check/?url=` — tells us whether the
+/// URL is already saved, plus scraped metadata and suggested tags for new saves.
+struct BookmarkCheck: Codable, Sendable {
+    let bookmark: Bookmark?
+    let metadata: Metadata?
+    let autoTags: [String]?
+
+    struct Metadata: Codable, Sendable {
+        let title: String?
+        let description: String?
+    }
+
+    enum CodingKeys: String, CodingKey {
+        case bookmark, metadata
+        case autoTags = "auto_tags"
+    }
+}
+
 struct BookmarkCreate: Codable, Sendable {
     let url: String
     let title: String
@@ -90,6 +108,14 @@ struct BookmarkUpdate: Codable, Sendable {
     }
 }
 
+struct LinkdingTag: Codable, Sendable {
+    let name: String
+}
+
+struct TagResponse: Codable, Sendable {
+    let results: [LinkdingTag]
+}
+
 struct SmartCollection: Identifiable, Sendable {
     let id = UUID()
     let name: String

Marks/Models/ServerConfig.swift

@@ -25,6 +25,13 @@ extension ServerConfig {
         return try? JSONDecoder().decode(ServerConfig.self, from: data)
     }
 
+    /// Loads config from the shared app group — used by extensions, which have no
+    /// access to the main app's `UserDefaults.standard`.
+    static func loadShared() -> ServerConfig? {
+        guard let data = UserDefaults(suiteName: appGroupId)?.data(forKey: key) else { return nil }
+        return try? JSONDecoder().decode(ServerConfig.self, from: data)
+    }
+
     func save() {
         guard let data = try? JSONEncoder().encode(self) else { return }
         UserDefaults.standard.set(data, forKey: ServerConfig.key)