feat: Add Windows compatibility, PyInstaller build setup, and custom icon

- Add Windows LibreOffice detection fallback for soffice path
  - Check standard install locations (%PROGRAMFILES%, %PROGRAMFILES(X86)%)
  - Graceful fallback with clear error messages

- Add PyInstaller build infrastructure
  - build/ccma.spec: PyInstaller configuration with icon generation
  - build/build.ps1: Automated build script for standalone exe
  - main.py: Entry point for PyInstaller
  - Supports versioning and architecture tagging

- Create custom CCMA icon
  - Person + Gear symbol representing member administration
  - Cyan/White/Orange color scheme
  - Auto-converts PNG to ICO during build

- Update documentation
  - README: Windows PowerShell setup instructions
  - README: Linux/macOS bash setup instructions
  - README: Standalone executable build guide
  - pyproject.toml: Add 'build' extra with pyinstaller+pillow

- Add regression tests
  - Test office executable detection and Windows fallback
  - Verify all tests pass (80 passed)

pyproject.toml

@@ -21,6 +21,10 @@ dev = [
     "pytest>=8",
     "ruff>=0.6",
 ]
+build = [
+    "pyinstaller>=6",
+    "pillow>=9",
+]
 
 [project.scripts]
 ccma = "ccma.app:main"