chore(terraform): add .gitignore — exclude tfstate and sensitive files

infrastructure/terraform/.gitignore

@@ -0,0 +1,22 @@
+# Terraform state — never commit
+*.tfstate
+*.tfstate.backup
+*.tfstate.*.backup
+
+# Terraform working directory
+.terraform/
+.terraform.lock.hcl
+
+# Sensitive variable files
+*.tfvars
+!terraform.tfvars.example
+
+# Crash logs
+crash.log
+crash.*.log
+
+# Override files
+override.tf
+override.tf.json
+*_override.tf
+*_override.tf.json