feat: Introduce iperf3 Kubernetes network monitor

Add core components for continuous cluster network validation:
- Python exporter (`exporter/`) to run iperf3 tests and expose Prometheus metrics.
- Helm chart (`charts/iperf3-monitor/`) for deploying the exporter as a
  Deployment and iperf3 server as a DaemonSet.
- CI/CD workflow (`.github/workflows/release.yml`) for building/publishing
  images and charts on tag creation.
- Initial documentation, license, and `.gitignore`.

.gitignore

@@ -0,0 +1,40 @@
+```
+# Byte-code files
+*.pyc
+*.pyo
+*.pyd
+__pycache__/
+
+# Distribution / build outputs
+dist/
+build/
+*.egg-info/
+.tox/
+
+# Virtual environments
+.venv/
+venv/
+env/
+
+# Editor/IDE specific files
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# Logs and temporary files
+*.log
+*.tmp
+
+# OS generated files
+.DS_Store
+Thumbs.db
+
+# Docker
+!Dockerfile
+.dockerignore
+
+# Helm
+!charts/iperf3-monitor/.helmignore
+charts/*.tgz # Ignore packaged chart files
+```