fix: add terraform.tf for pre-commit validation

Required for tofu-validate and tflint to work standalone
without the terragrunt-generated backend.tf.

modules/gitea_instance/terraform.tf

@@ -0,0 +1,13 @@
+terraform {
+  required_version = ">= 1.10"
+  required_providers {
+    gitea = {
+      source  = "go-gitea/gitea"
+      version = "0.7.0"
+    }
+    woodpecker = {
+      source  = "Kichiyaki/woodpecker"
+      version = "0.5.0"
+    }
+  }
+}