feat: add zip packaging target and woodpecker release pipeline

- Makefile gains `make package` target that builds and zips the provider
  binary in the format expected by artifactapi's local terraform registry:
  terraform-provider-artifactapi_{version}_{os}_{arch}.zip
- New .woodpecker/release.yml pipeline triggers on tag push, builds the
  zip, and uploads it to artifactapi via the local files API
- Secrets: artifactapi_url and artifactapi_repo

Makefile

@@ -1,9 +1,11 @@
-.PHONY: build install test lint fmt clean tidy
+.PHONY: build install test lint fmt clean tidy package
 
 BINARY := terraform-provider-artifactapi
 VERSION ?= 0.0.1
 OS_ARCH := linux_amd64
-INSTALL_DIR := ~/.terraform.d/plugins/git.unkin.net/unkin/artifactapi/$(VERSION)/$(OS_ARCH)
+INSTALL_VERSION := $(shell echo $(VERSION) | sed 's/^v//')
+INSTALL_DIR := ~/.terraform.d/plugins/git.unkin.net/unkin/artifactapi/$(INSTALL_VERSION)/$(OS_ARCH)
+ZIP := $(BINARY)_$(INSTALL_VERSION)_$(OS_ARCH).zip
 
 GO_VERSION_REQUIRED := 1.23
 GO_VERSION_ACTUAL := $(shell go version | sed 's/go version go\([0-9]*\.[0-9]*\).*/\1/')
@@ -29,8 +31,13 @@ lint: check-go
 fmt: check-go
 	gofmt -w .
 
+package: build
+	cp $(BINARY) $(BINARY)_v$(INSTALL_VERSION)
+	zip $(ZIP) $(BINARY)_v$(INSTALL_VERSION)
+	rm $(BINARY)_v$(INSTALL_VERSION)
+
 clean:
-	rm -f $(BINARY)
+	rm -f $(BINARY) *.zip
 
 tidy:
 	go mod tidy