feat: initial terraform provider for artifactapi v0.0.1

Resources:
- artifactapi_remote: CRUD for remote proxy repositories
- artifactapi_virtual: CRUD for virtual (merged) repositories

Data sources:
- data.artifactapi_remote: read remote config
- data.artifactapi_virtual: read virtual config

Supports all 10 package types (generic, docker, helm, pypi, npm,
rpm, alpine, puppet, terraform, goproxy), allowlist/blocklist,
tag banning, quarantine, and terraform import.

.gitignore

@@ -0,0 +1,4 @@
+terraform-provider-artifactapi
+.terraform/
+*.tfstate
+*.tfstate.backup