feat(dragonfly): add injector support to helm chart

[pmady]

What type of PR is this?

enhancement

What this PR does / why we need it:

This PR adds support for the Dragonfly Injector component to the Dragonfly Helm chart. The injector is a Kubernetes mutating webhook that automatically injects Dragonfly P2P proxy settings, dfdaemon socket mounts, and CLI tools into pods based on namespace labels.

Which issue(s) this PR fixes:

Related to dragonflyoss/dragonfly#4524

Special notes for your reviewer:

New Components Added:

• Deployment: Injector deployment with configurable replicas, resources, and security context
• Service: Webhook service exposing ports 443 (webhook) and 8443 (metrics)
• RBAC: ServiceAccount, ClusterRole, ClusterRoleBinding, Role, and RoleBinding for leader election
• ConfigMap: Injector configuration (proxy port, CLI tools image, etc.)
• Certificate: cert-manager Certificate and Issuer for webhook TLS
• MutatingWebhookConfiguration: Webhook configuration with namespace selector

Configuration:

The injector is disabled by default. Enable it with:

injector:
  enable: true

Prerequisites:

• cert-manager must be installed for automatic TLS certificate management

Does this PR introduce a user-facing change?

Add injector support to Dragonfly Helm chart for automatic pod injection of P2P proxy settings

[pmady]

Related PR for injector dragonflyoss/dragonfly#4524

[pmady]

Hi maintainers, could you please add the enhancement label to this PR? The PR Label check requires one of: bug, enhancement, documentation, or dependencies. Thank you!