feat: add terraform-local package type for local registry

- New package type "terraform-local" for hosting terraform providers
  without an upstream registry
- Upload via PUT /api/v2/remotes/{name}/files/{path}, returns 409 on
  duplicate (overwrites not allowed)
- Download via GET on same path, or via v1 proxy route
- Provider registers as fully immutable, no upstream rewriting
- v1 proxy handler serves local files directly for local repo types
- Database CRUD for local_files table

pkg/models/package_type.go

@@ -13,8 +13,9 @@ const (
 	PackageRPM       PackageType = "rpm"
 	PackageAlpine    PackageType = "alpine"
 	PackagePuppet    PackageType = "puppet"
-	PackageTerraform PackageType = "terraform"
-	PackageGoProxy   PackageType = "goproxy"
+	PackageTerraform      PackageType = "terraform"
+	PackageTerraformLocal PackageType = "terraform-local"
+	PackageGoProxy        PackageType = "goproxy"
 )
 
 var validPackageTypes = map[PackageType]bool{
@@ -26,14 +27,19 @@ var validPackageTypes = map[PackageType]bool{
 	PackageRPM:       true,
 	PackageAlpine:    true,
 	PackagePuppet:    true,
-	PackageTerraform: true,
-	PackageGoProxy:   true,
+	PackageTerraform:      true,
+	PackageTerraformLocal: true,
+	PackageGoProxy:        true,
 }
 
 func (p PackageType) Valid() bool {
 	return validPackageTypes[p]
 }
 
+func (p PackageType) IsLocal() bool {
+	return p == PackageTerraformLocal
+}
+
 func (p PackageType) String() string {
 	return string(p)
 }