Add rack image and SC diagram SVG

- Added a new image file for the rack located at feature/rack/rack.png.
- Introduced a new SVG file for the SC diagram at now/phys/sc-diagram.drawio.svg, containing detailed graphical representations of network components and their connections.

.gitignore

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+# OS-generated files
+Thumbs.db
+ehthumbs.db
+Desktop.ini
+.DS_Store
+
+# Visual Studio / VS Code local settings (keep general workspace settings, ignore local-only files)
+.vscode/*.code-workspace
+.vscode/*history*
+.vscode/*.db
+.vscode/mcp.json
+*.prompt.md
+
+# IDEs
+.idea/
+
+# Python
+__pycache__/
+*.py[cod]
+*.pyo
+*.pyd
+env/
+venv/
+ENV/
+.Python
+
+# Node
+node_modules/
+
+# Build / distribution
+dist/
+build/
+out/
+
+# Logs
+*.log
+
+# Archives and common binaries
+*.zip
+*.tar.gz
+*.7z
+*.exe
+*.dll
+*.so
+
+# 3D assets and large binary files (usually generated or large — keep out of repo unless intentional)
+*.blend
+*.blend1
+*.fbx
+*.obj
+*.stl
+
+# Temporary/backups
+*.tmp
+*.bak
+~$*