Introduce Goreleaser (#366)

<!-- Provide a brief summary of your changes -->

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The following PR introduces Goreleaser for the releases of the registry
server and the publisher CLI.

**Details:**
- Builds registry and publisher binaries for Linux, macOS, and Windows
(amd64 + arm64)
- Leverage GitHub's release process by creating releases directly from
GitHub's interface
- Added .goreleaser.yaml configuration
- New .github/workflows/release.yml workflow triggered by GitHub
releases
- Updated Docker tagging in deploy workflow (:latest and :semver(the
tag) for releases, :main-YYYYMMDD-sha for testing/development)
- Consolidated version handling in main.go files
- Added release documentation

## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->

Locally (but we have to test it by creating a release, i.e. v0.0.1 once
this gets merged)

## Breaking Changes
<!-- Will users need to update their code or configurations? -->
Yes, the notion of `latest` for the container image is now different

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->
Related to #358

---------

Signed-off-by: Radoslav Dimitrov <radoslav@stacklok.com>

Makefile

@@ -6,11 +6,13 @@ help: ## Show this help message
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "  %-20s %s\n", $$1, $$2}'
 
 # Build targets
-build: ## Build the registry application
-	go build -o bin/registry ./cmd/registry
+build: ## Build the registry application with version info
+	@mkdir -p bin
+	go build -ldflags="-X main.Version=dev-$(shell git rev-parse --short HEAD) -X main.GitCommit=$(shell git rev-parse HEAD) -X main.BuildTime=$(shell date -u +%Y-%m-%dT%H:%M:%SZ)" -o bin/registry ./cmd/registry
 
-publisher: ## Build the publisher tool
-	cd cmd/publisher && ./build.sh
+publisher: ## Build the publisher tool with version info
+	@mkdir -p bin
+	go build -ldflags="-X main.Version=dev-$(shell git rev-parse --short HEAD) -X main.GitCommit=$(shell git rev-parse HEAD) -X main.BuildTime=$(shell date -u +%Y-%m-%dT%H:%M:%SZ)" -o bin/mcp-publisher ./cmd/publisher
 
 # Test targets
 test-unit: ## Run unit tests with coverage
@@ -64,7 +66,6 @@ dev-local: ## Run registry locally
 clean: ## Clean build artifacts and coverage files
 	rm -rf bin
 	rm -f coverage.out coverage.html
-	cd cmd/publisher && rm -f publisher
 
 
 .DEFAULT_GOAL := help