Use ko in favour of docker build (#708)

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

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The following PR leverages ko instead of docker build for building the
container image.

The motivation for the move is that ko has been one of the widely
adopted ways to build Go applications, but overall its benefits are:
* Build time is much faster - around 70-80%
* The resulting image size is much smaller (also more secure) - around
50% smaller

The changes in this PR are:
* Updated the workflows for staging and release to prod to use it
* Updated the local development + the integration tests to use it (the
integration tests overwrite the base image from chainguards one to
alpine mostly because we rely on wget to check the health status and you
don't get that in the stripped down one)
 
From the user point of view everything should continue to work as it is.
 
## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->

## Breaking Changes
<!-- Will users need to update their code or configurations? -->

## 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)
- [ ] 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
-->

---------

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

Makefile

@@ -1,4 +1,4 @@
-.PHONY: help build test test-unit test-integration test-endpoints test-publish test-all lint lint-fix validate validate-schemas validate-examples check dev-compose clean publisher generate-schema check-schema
+.PHONY: help build test test-unit test-integration test-endpoints test-publish test-all lint lint-fix validate validate-schemas validate-examples check ko-build ko-rebuild dev-compose dev-down clean publisher generate-schema check-schema
 
 # Default target
 help: ## Show this help message
@@ -83,11 +83,23 @@ check: dev-down lint validate test-all ## Run all checks (lint, validate, unit t
 	@echo "All checks passed!"
 
 # Development targets
-dev-compose: ## Start development environment with Docker Compose (builds image automatically)
+ko-build: ## Build registry image using ko (loads into local docker daemon)
+	@echo "Building registry with ko..."
+	VERSION=dev-$$(git rev-parse --short HEAD) \
 	GIT_COMMIT=$$(git rev-parse HEAD) \
-	GIT_COMMIT_SHORT=$$(git rev-parse --short HEAD) \
 	BUILD_TIME=$$(date -u +%Y-%m-%dT%H:%M:%SZ) \
-	docker compose up --build
+	KO_DOCKER_REPO=ko.local \
+	ko build --preserve-import-paths --tags=dev --sbom=none ./cmd/registry
+	@echo "Image built: ko.local/github.com/modelcontextprotocol/registry/cmd/registry:dev"
+
+ko-rebuild: ## Rebuild with ko and restart registry container
+	@$(MAKE) ko-build
+	@echo "Restarting registry container..."
+	@docker compose restart registry
+
+dev-compose: ko-build ## Start development environment with Docker Compose (builds with ko first)
+	@echo "Starting Docker Compose..."
+	docker compose up
 
 dev-down: ## Stop development environment
 	docker compose down