Overhaul VirtFusion provider: 20 resources, 30 data sources, multipage pagination

Complete rewrite of the VirtFusion Terraform provider with full API coverage:

- 20 managed resources (server, build, SSH key, user, firewall, IP blocks, etc.)
- 30 data sources (hypervisors, packages, servers, IP blocks, self-service, etc.)
- New HTTP client with proper error handling, query parameter support, and
  automatic multipage pagination via GetAllPages (fetches all pages from
  Laravel-style paginated endpoints and merges into a single response)
- Fixed type mismatches against live API: ServerData.Suspended (int→bool),
  IPBlockData.Type (string→int), PackageData json tags (primaryStorage, etc.),
  ServerData nested CPU/Settings/Resources structure, HypervisorGroupResources
  array response
- Configurable results-per-page (default 300) on all list data sources
- Migrated CI from GitHub Actions to Gitea Actions
- Updated goreleaser config, go.mod dependencies, and examples

Verified against live VirtFusion instance at cp.vps.ezscale.tech:
all data sources return correct data with full pagination support.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

examples/data-sources/scaffolding_example/data-source.tf

@@ -1,3 +0,0 @@
-data "scaffolding_example" "example" {
-  configurable_attribute = "some-value"
-}

examples/data-sources/virtfusion_hypervisors/data-source.tf

@@ -0,0 +1,5 @@
+data "virtfusion_hypervisors" "all" {}
+
+output "hypervisor_names" {
+  value = [for h in data.virtfusion_hypervisors.all.hypervisors : h.name]
+}

examples/data-sources/virtfusion_packages/data-source.tf

@@ -0,0 +1,5 @@
+data "virtfusion_packages" "all" {}
+
+output "package_names" {
+  value = [for p in data.virtfusion_packages.all.packages : p.name]
+}

examples/data-sources/virtfusion_server/data-source.tf

@@ -0,0 +1,7 @@
+data "virtfusion_server" "example" {
+  id = 1
+}
+
+output "server_name" {
+  value = data.virtfusion_server.example.name
+}