feat: Implement default welcome page for missing web application

- Added a professional HTML welcome page displayed when no web application is configured.
- Enhanced `_load_webapp()` method to support improved path resolution for both development and bundled modes.
- Updated error handling to show the welcome page instead of a bare error message when the webapp file is not found.
- Modified unit tests to verify the welcome page is displayed in error scenarios.

build: Complete Windows and macOS build scripts

- Created `build_windows.py` for building Windows executable and optional MSI installer using PyInstaller.
- Developed `build_macos.sh` for creating macOS application bundle and DMG image.
- Added logging and error handling to build scripts for better user feedback.

docs: Add build and icon requirements documentation

- Created `PHASE_3_BUILD_SUMMARY.md` detailing the build process, results, and next steps.
- Added `resources/icons/README.md` outlining icon requirements and creation guidelines.

chore: Sync remotes script for repository maintenance

- Introduced `sync_remotes.ps1` PowerShell script to fetch updates from origin and upstream remotes.

.gitignore

@@ -8,7 +8,10 @@ __pycache__/
 
 # Distribution / packaging
 .Python
-build/
+build/dist/
+build/windows/
+build/macos/
+build/temp/
 develop-eggs/
 dist/
 downloads/