feat(ios): add share to support (#15340)

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

* **New Features**
  * Added iOS sharing for URLs, text, web pages, and images.
* Shared content can be reviewed, titled, and saved to an AFFiNE
workspace.
  * Choose destinations including workspaces, tags, and collections.
* Added previews, attachment handling, import status, retry support, and
success/error feedback.
* Pending shares are processed when AFFiNE opens or returns to the
foreground.
* **Bug Fixes**
* Improved workspace profile handling across different workspace types.
* Onboarding completion is now recorded immediately after successful
sign-in verification.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: DarkSky <25152247+darkskygit@users.noreply.github.com>

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

@@ -0,0 +1,79 @@
+import SwiftUI
+
+struct ShareExtensionView: View {
+  @ObservedObject var viewModel: ShareViewModel
+  var onCancel: () -> Void
+  var onSave: () -> Void
+
+  var body: some View {
+    NavigationStack {
+      Group {
+        if viewModel.isLoading {
+          ProgressView("Reading shared content…")
+            .frame(maxWidth: .infinity, maxHeight: .infinity)
+        } else {
+          content
+        }
+      }
+      .navigationTitle("AFFiNE")
+      .navigationBarTitleDisplayMode(.inline)
+      .toolbar {
+        ToolbarItem(placement: .cancellationAction) {
+          Button("Not now", action: onCancel)
+            .disabled(viewModel.isSaving)
+        }
+        ToolbarItem(placement: .confirmationAction) {
+          if viewModel.isSaving {
+            ProgressView()
+          } else {
+            Button(viewModel.actionTitle, action: onSave)
+              .fontWeight(.semibold)
+              .disabled(!viewModel.canSave)
+          }
+        }
+      }
+    }
+  }
+
+  private var content: some View {
+    Form {
+      Section {
+        Text("Choose a workspace in AFFiNE. This item will stay saved until then.")
+          .font(.footnote)
+          .foregroundStyle(.secondary)
+      }
+
+      Section {
+        HStack(alignment: .top, spacing: 12) {
+          Image(systemName: viewModel.previewImage == nil ? "doc.text" : "photo")
+            .font(.title2)
+            .frame(width: 32, height: 32)
+            .foregroundStyle(.secondary)
+          VStack(alignment: .leading, spacing: 4) {
+            TextField("Title", text: $viewModel.title)
+              .font(.headline)
+            if !viewModel.previewText.isEmpty {
+              Text(viewModel.previewText)
+                .lineLimit(3)
+                .font(.subheadline)
+                .foregroundStyle(.secondary)
+            }
+          }
+        }
+        if let image = viewModel.previewImage {
+          Image(uiImage: image)
+            .resizable()
+            .scaledToFit()
+            .frame(maxHeight: 180)
+        }
+      }
+
+      if let errorMessage = viewModel.errorMessage {
+        Section {
+          Text(errorMessage)
+            .foregroundStyle(.red)
+        }
+      }
+    }
+  }
+}