feat: Helm chart for Kubernetes deployment

[eric-becker]

Feature request

Create a Helm chart for deploying floodgate on Kubernetes, replacing the static manifests in k8s/.

Benefits over static manifests

• Parameterized config (channel policy, log format, ports) via values.yaml
• Easy upgrades with helm upgrade and built-in rollback
• Rolling update support out of the box
• Templated ConfigMap, Deployment, Service
• Publishable to a Helm repo for one-line installs

Scope

• Chart in charts/floodgate/
• Templates for: Deployment, Service (ClusterIP), ConfigMap, ServiceAccount
• values.yaml with all config options from config.yaml
• Support for custom channel_blacklist / channel_whitelist via values
• Security context matching current k8s manifests (nonroot, read-only fs, drop caps)
• Optional PodDisruptionBudget
• README with install/upgrade instructions

Out of scope (for now)

• EMQX deployment (separate chart exists)
• ExHook registration automation
• TLS for gRPC