feat(ios): implement offline mode & sync conflict resolution (#23)

- Add OfflineSyncCoordinator for managing offline/online transitions
- Add OfflineSyncIndicatorView for UI feedback during sync
- Add SyncProgress tracking with stage descriptions and progress bars
- Add delta sync support with savings tracking
- Add BackgroundTaskScheduler interval configs for low-power mode
- Add isProcessingTask discriminator to BackgroundTaskID
- Add DeltaFetchResult generic type for efficient data fetching
- Add SyncProgressStage enum with localized descriptions
- Add progress reset on app launch to prevent stale state
- Add delta sync savings percentage calculation
- Update BackgroundSyncTests with comprehensive coverage
- Add OfflineSyncTests for offline queue and conflict resolution
- Mark task 22 (Token Refresh) and task 28 (Review Compliance) as done
- Update Xcode project with new source files and build phases

iOS/Kordant.xcodeproj/xcshareddata/xcschemes/Kordant.xcscheme

@@ -21,6 +21,20 @@
                ReferencedContainer = "container:Kordant.xcodeproj">
             </BuildableReference>
          </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "9F565239D0F660D3DBD9FB02"
+               BuildableName = "KordantSpamShieldExtension.appex"
+               BlueprintName = "KordantSpamShieldExtension"
+               ReferencedContainer = "container:Kordant.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
          <BuildActionEntry
             buildForTesting = "YES"
             buildForRunning = "NO"