chore(release): prepare v0.5.0-beta (#148)

This commit prepares the repository for the v0.5.0-beta release,
transitioning from alpha to beta status.

Changes made:
- Update version from 0.4.1-alpha to 0.5.0-beta in version.py
- Update Development Status classifier from Alpha to Beta in pyproject.toml and setup.py
- Update status badges from Alpha (orange) to Beta (blue) in README.md
- Update all installation command examples to use v0.5.0-beta tag
- Update release announcement from Alpha to Beta in README.md
- Add RELEASE_PROCESS.md documentation for future releases
- Update docs/INSTALL.md with new version references
- Add What's New section for v0.5.0-beta in docs/UPDATE.md
- Update SECURITY.md supported versions table
- Update website schema softwareVersion in layout.tsx
- Update website version badges in page.tsx
- Update website package.json version to 0.5.0

Testing:
- All 463 tests passing (100%)
- Version consistency verified across all files

Release process documentation added to docs/RELEASE_PROCESS.md

setup.py

@@ -138,7 +138,7 @@ setup(
     ],
     include_package_data=True,
     classifiers=[
-        "Development Status :: 3 - Alpha",
+        "Development Status :: 4 - Beta",
         "Environment :: X11 Applications :: GTK",
         "Intended Audience :: End Users/Desktop",
         "License :: OSI Approved :: GNU General Public License v3 (GPLv3)",