docs: update changelog with Sparkle updater fixes and improvements

Document the key fixes that made Sparkle updates work:
- Using ditto instead of zip to preserve code signatures
- XPC service entitlements for sandboxed apps
- In-app logging for update debugging
- Re-enabled sandbox with minimal entitlements

CHANGELOG.md

@@ -1,6 +1,24 @@
 # Changelog
 
 ## Unreleased
+
+### Fixed
+- Fixed Sparkle updater ZIP archive creation: replaced `zip` command with `ditto` to properly preserve app bundle code signatures during extraction, resolving "damaged app" errors on update installation.
+- Fixed code signature issues for sandboxed apps by removing entitlements parameter from non-sandboxed builds.
+- Fixed Sparkle framework deep code signing to handle complex framework structure.
+- Fixed missing XPC service entitlements (`com.apple.security.xpc.aConnectionServices`, `com.apple.security.xpc.aStatusServices`) required for Sparkle installer to communicate with sandboxed app.
+
+### Changed
+- Re-enabled app sandbox with minimal entitlements (network.client only) for improved security while maintaining Sparkle update functionality.
+- Enhanced Sparkle error logging to include error domain and code information, making update failures easier to diagnose.
+- Updated build script to use `ditto -c -k --keepParent` for creating update ZIPs, which properly preserves code signatures that `zip` command breaks.
+
+### Added
+- Added in-app Sparkle update logs in Preferences → Updates tab with Show/Hide toggle for real-time debugging of update operations.
+- Log entries include timestamps and distinguish between info and error messages.
+- Users can clear logs manually and logs persist during the session (max 100 entries).
+
+### Previous Changes
 - Flattened the project structure so sources live at the repository root instead of the nested `iKeyMon/` folder and updated the Xcode project accordingly.
 - Fixed build settings (entitlements, preview assets) and placeholder previews to work with the new layout.
 - Migrated the updated API layer and unified `ServerInfo` model from the previous branch.
@@ -10,5 +28,5 @@
 - Introduced repository-wide version management via `version.json` + `scripts/sync_version.sh`, ensuring Xcode targets and release artifacts stay aligned.
 - Enhanced `scripts/build_release.sh` to timestamp/harden signatures, notarize DMGs, and optionally publish tagged releases (pre-release by default) with ZIP/DMG assets directly to Gitea when credentials are configured.
 - Integrated Sparkle (via Swift Package Manager) to handle automatic update checks, downloads, signature verification, and relaunches, replacing the previous custom updater UI. Preferences now simply surface Sparkle's check/download toggles.
-- `scripts/build_release.sh` can optionally run Sparkle’s `generate_appcast` (when signing key and download prefix env vars are set), producing a ready-to-host `appcast.xml` alongside the ZIP/DMG artifacts.
+- `scripts/build_release.sh` can optionally run Sparkle's `generate_appcast` (when signing key and download prefix env vars are set), producing a ready-to-host `appcast.xml` alongside the ZIP/DMG artifacts.
 - Further reduced MainView console noise by removing redundant refresh/onAppear logs.