Add local_generic rootfs-images repository

Declares a local generic (raw-file) repo for bootapi's node rootfs tarballs and
wires the local_generic kind through the module. Depends on
terraform-provider-artifactapi #12 releasing v0.1.4 (adds artifactapi_local_generic);
the provider version pin is bumped to 0.1.4, so plan/validate stay red until that
release is available.

- config/local_generic/rootfs-images.yaml (new repo).
- local_generic wiring: config.hcl, module variables.tf + main.tf, env
  terragrunt.hcl inputs; provider pin 0.1.3 -> 0.1.4.

Claude-Session: https://claude.ai/code/session_015ur3i7D2azsMAWTSVABApv

modules/artifactapi/versions.tf

@@ -3,7 +3,7 @@ terraform {
   required_providers {
     artifactapi = {
       source  = "artifactapi.k8s.syd1.au.unkin.net/terraform-unkin/artifactapi"
-      version = "0.1.3"
+      version = "0.1.4"
     }
   }
 }