Add SSO login support

- Add [sso] config section with redirect_uri
- Create mcdsl/sso client when SSO is configured
- Add /login (landing page), /sso/redirect, /sso/callback routes
- Add /logout route
- Update login template with SSO landing page variant
- Bump mcdsl to v1.6.0

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

vendor/github.com/go-chi/chi/v5/Makefile

@@ -0,0 +1,22 @@
+.PHONY: all
+all:
+	@echo "**********************************************************"
+	@echo "**                    chi build tool                    **"
+	@echo "**********************************************************"
+
+
+.PHONY: test
+test:
+	go clean -testcache && $(MAKE) test-router && $(MAKE) test-middleware
+
+.PHONY: test-router
+test-router:
+	go test -race -v .
+
+.PHONY: test-middleware
+test-middleware:
+	go test -race -v ./middleware
+
+.PHONY: docs
+docs:
+	npx docsify-cli serve ./docs