feat: add standalone launchers and fix model path resolution

[zeeshanhayat123]

• Add run_hy3d.py bootstrap launcher that strips Hermes PYTHONPATH pollution before importing hy3dgen modules
• Add run_hy3d.bat Windows CLI wrapper (venv python, clean env)
• Add run_hy3d_web.bat Gradio web UI launcher with offline mode
• Fix smart_load_model: expanduser now applies to base_dir only (was incorrectly wrapping the joined path), added normpath for consistent Windows path handling
• Ignore models/ directory in git to exclude multi-GB cache

[tencent-adm]

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[4dithyan]

Yeeeee