feat(ci,iac): Consolidate Forgejo CI workflows and add Talos Terraform IaC

Consolidate three separate Forgejo Actions (argocd-sync, security-scan, validate-k8s) into single cluster-ci workflow for cleaner CI/CD pipeline with proper job sequencing and reduced auth overhead.

Add Terraform configuration for Talos cluster machine configs:
- Provider setup for Talos
- Centralized variables for CP and worker configs
- Template-based config generation for controlplane.yaml and worker-*.yaml
- Sensitive data separated in terraform.tfvars (gitignored)
- Local state tracking for infrastructure

terraform/provider.tf

@@ -0,0 +1,12 @@
+terraform {
+  required_providers {
+    talos = {
+      source  = "siderolabs/talos"
+      version = "~> 0.7"
+    }
+  }
+
+  required_version = ">= 1.0"
+}
+
+provider "talos" {}