feat(ios): improve share preview (#15538)

#### PR Dependency Tree

* **PR #15538** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added rich link previews to mobile and iOS sharing, including images,
metadata, transcripts, and selected text.
* Share imports can now create structured content blocks, embeds,
bookmarks, and transcript callouts.
* Added workspace-aware preview handling for cloud, self-hosted, and
signed-out modes.
* **Accessibility**
* Improved collapse/expand controls with semantic buttons and ARIA
relationships.
* **Bug Fixes**
  * Enhanced URL and error sanitization in server logs.
* Improved link-preview CORS support, validation, and request handling.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/apps/ios/App/ShareExtension/ShareViewModel.swift

@@ -10,6 +10,9 @@ final class ShareViewModel: ObservableObject {
   @Published var isSaving = false
   @Published var hasSaved = false
   @Published var errorMessage: String?
+  @Published var linkPreviewState: ShareLinkPreviewState = .idle
+  @Published var linkPreviewMediaImage: UIImage?
+  @Published var linkPreviewFaviconImage: UIImage?
 
   var actionTitle: String {
     "Open AFFiNE"
@@ -23,10 +26,43 @@ final class ShareViewModel: ObservableObject {
   }
 
   private var draft: SharePayloadDraft?
+  private var previewRoute: SharePreviewRoute = .deferred
+  private var previewTask: Task<Void, Never>?
+  private var userEditedTitle: String?
   private let store: ShareInboxStore
+  private let previewClient: ShareLinkPreviewClient
 
-  init(store: ShareInboxStore = .shared) {
+  init(
+    store: ShareInboxStore = .shared,
+    previewClient: ShareLinkPreviewClient = ShareLinkPreviewClient()
+  ) {
     self.store = store
+    self.previewClient = previewClient
+  }
+
+  var linkPreview: ShareLinkPreview? {
+    guard case let .loaded(preview) = linkPreviewState else { return nil }
+    return preview
+  }
+
+  var displayTitle: String {
+    ShareInboxSafety.previewTitle(
+      original: title,
+      userEdited: userEditedTitle,
+      serverTitle: linkPreview?.title
+    )
+  }
+
+  var sharedURL: String? { draft?.content?.url }
+
+  var selectedText: String? {
+    guard draft?.content?.kind == .url else { return nil }
+    return draft?.content?.text
+  }
+
+  func updateTitle(_ value: String) {
+    userEditedTitle = value
+    title = value
   }
 
   func load(from extensionContext: NSExtensionContext?) async {
@@ -36,21 +72,54 @@ final class ShareViewModel: ObservableObject {
     let items = extensionContext?.inputItems.compactMap { $0 as? NSExtensionItem } ?? []
     let built = await SharePayloadBuilder.build(from: items)
     draft = built
+    userEditedTitle = nil
     title = built.title
     previewText = built.previewText
     errorMessage = built.errorMessage
+    linkPreviewMediaImage = nil
+    linkPreviewFaviconImage = nil
     if let file = built.file {
       previewImage = UIImage(data: file.data)?
         .preparingThumbnail(of: CGSize(width: 480, height: 480))
     }
+    guard built.content?.kind == .url, let url = built.content?.url else { return }
+    previewRoute = ShareInboxSafety.previewRoute(mode: store.workspaceMode(), url: url)
+    guard previewRoute == .official else {
+      linkPreviewState = .deferred
+      return
+    }
+    linkPreviewState = .loading
+    previewTask = Task { [weak self] in
+      guard let self else { return }
+      do {
+        let preview = try await previewClient.fetch(url: url)
+        guard !Task.isCancelled else { return }
+        linkPreviewState = .loaded(preview)
+        async let media = previewClient.fetchImageIfPresent(url: preview.images?.first)
+        async let favicon = previewClient.fetchImageIfPresent(url: preview.favicons?.first)
+        let images = await (media, favicon)
+        guard !Task.isCancelled else { return }
+        linkPreviewMediaImage = images.0
+        linkPreviewFaviconImage = images.1
+      } catch is CancellationError {
+        return
+      } catch {
+        guard !Task.isCancelled else { return }
+        linkPreviewState = .failed
+      }
+    }
   }
 
   func save() async -> Bool {
     guard !isSaving, !hasSaved else { return false }
+    previewTask?.cancel()
     isSaving = true
     defer { isSaving = false }
 
-    let trimmedTitle = title.trimmingCharacters(in: .whitespacesAndNewlines)
+    let trimmedTitle = ShareInboxSafety.manifestTitle(
+      original: draft?.title ?? title,
+      userEdited: userEditedTitle
+    )
     guard !trimmedTitle.isEmpty else {
       errorMessage = "Title is required."
       return false
@@ -77,6 +146,7 @@ final class ShareViewModel: ObservableObject {
       id: itemId,
       title: trimmedTitle,
       content: content,
+      previewRoute: previewRoute,
       previewText: draft.previewText,
       attachments: attachments
     )