Add GitHub Actions CI/CD workflows and documentation

- Add Docker image build and push workflow (multi-arch: amd64, arm64)
- Add Helm chart release workflow with GitHub Pages publishing
- Add comprehensive release workflow for version tags
- Add PR validation workflow (tests, linting, validation)
- Update Chart.yaml and values.yaml with GitHub URLs
- Update image repository to use ghcr.io
- Add detailed CI/CD documentation and setup guides

Workflows provide:
- Automated Docker image builds to GitHub Container Registry
- Automated Helm chart releases to GitHub Pages
- Complete release automation with version tagging
- PR validation with tests and linting

Helm repository will be available at:
https://vegardengen.github.io/unifi-network-operator

Docker images available at:
ghcr.io/vegardengen/unifi-network-operator

helm/unifi-network-operator/Chart.yaml

@@ -4,13 +4,15 @@ description: A Kubernetes operator for managing UniFi network configurations
 type: application
 version: 0.1.0
 appVersion: "latest"
-home: https://github.com/yourusername/unifi-network-operator
+home: https://github.com/vegardengen/unifi-network-operator
 maintainers:
   - name: Vegar Dengen
+    url: https://github.com/vegardengen
 keywords:
   - unifi
   - network
   - operator
   - firewall
+  - ubiquiti
 sources:
-  - https://github.com/yourusername/unifi-network-operator
+  - https://github.com/vegardengen/unifi-network-operator

helm/unifi-network-operator/values.yaml

@@ -5,7 +5,7 @@ replicaCount: 1
 
 image:
   # -- Container image repository
-  repository: gitea.engen.priv.no/klauvsteinen/unifi-network-operator-controller
+  repository: ghcr.io/vegardengen/unifi-network-operator
   # -- Image pull policy
   pullPolicy: IfNotPresent
   # -- Overrides the image tag whose default is the chart appVersion