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/Services/LinkdingAPI.swift

@@ -78,6 +78,28 @@ actor LinkdingAPI {
         return try decoder.decode(BookmarkResponse.self, from: data)
     }
 
+    /// Checks whether `url` is already bookmarked. Returns the existing bookmark
+    /// (or nil), scraped metadata, and suggested tags for a fresh save.
+    func checkBookmark(url urlString: String) async throws -> BookmarkCheck {
+        let url = try makeUrl(path: "/api/bookmarks/check/", queryItems: [.init(name: "url", value: urlString)])
+        let (data, response) = try await session.data(for: authorizedRequest(url: url))
+        guard (response as? HTTPURLResponse)?.statusCode == 200 else {
+            throw APIError.badStatus((response as? HTTPURLResponse)?.statusCode ?? 0)
+        }
+        return try decoder.decode(BookmarkCheck.self, from: data)
+    }
+
+    /// All tag names the user already uses — the existing vocabulary we bias
+    /// AI tag suggestions toward.
+    func fetchTags(limit: Int = 1000) async throws -> [String] {
+        let url = try makeUrl(path: "/api/tags/", queryItems: [.init(name: "limit", value: "\(limit)")])
+        let (data, response) = try await session.data(for: authorizedRequest(url: url))
+        guard (response as? HTTPURLResponse)?.statusCode == 200 else {
+            throw APIError.badStatus((response as? HTTPURLResponse)?.statusCode ?? 0)
+        }
+        return try decoder.decode(TagResponse.self, from: data).results.map(\.name)
+    }
+
     func createBookmark(_ create: BookmarkCreate) async throws -> Bookmark {
         let body = try JSONEncoder().encode(create)
         let url = try makeUrl(path: "/api/bookmarks/")