feat: integrate KordantSpamShieldExtension target and complete App Review compliance (Task 28)

- Add KordantSpamShieldExtension target to project.yml with proper
  app-extension type, bundle identifier, and deployment target
- Create CallKit + App Group entitlements for SpamShield extension
- Move SpamDirectoryService to Sources/Shared for cross-target access
- Update app-review-checklist with 5 new technical items (total: 121)
- Update rejection-risk-mitigation with extension build integration
- Add SpamShield extension details to reviewer notes
- Mark Task 24 (push deep links) and Task 28 as complete

iOS/docs/rejection-risk-mitigation.md

@@ -138,11 +138,14 @@
 
 ### Call Directory Extension
 
-**Risk**: Extension not enabled by reviewer  
+**Risk**: Extension not properly integrated in build  
 **Mitigation**:
+- ✅ Extension target added to `project.yml` with proper configuration
+- ✅ Entitlements created (CallKit + App Group) for shared data access
+- ✅ `SpamDirectoryService` moved to `Sources/Shared` for cross-target access
 - ✅ Extension is optional — app works without it
 - ✅ Clear instructions in SpamShield settings
-- ✅ Extension status shown in settings
+- ✅ Extension status checked via `CXCallDirectoryManager.getEnabledStatusForExtension`
 - ✅ Graceful fallback when extension is not enabled
 
 ---
@@ -211,6 +214,8 @@ Before submitting to App Store Review:
 
 - [ ] Build Release configuration
 - [ ] Verify no `#if DEBUG` code paths contain visible content
+- [ ] Verify no `print()` calls remain outside `#Preview` blocks
+- [ ] Verify no force unwraps in production code paths
 - [ ] Test on physical device (not just simulator)
 - [ ] Verify all deep links work
 - [ ] Verify push notifications work
@@ -225,6 +230,8 @@ Before submitting to App Store Review:
 - [ ] Verify privacy policy URL works
 - [ ] Verify all screenshots match current app UI
 - [ ] Verify app preview video is current
+- [ ] Verify SpamShield extension target built
+- [ ] Verify SpamShield extension entitlements correct
 - [ ] Upload via Xcode Organizer or Transporter
 - [ ] Fill in App Store Connect metadata
 - [ ] Add review notes and demo account