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/spf13/cobra/Makefile

@@ -0,0 +1,35 @@
+BIN="./bin"
+SRC=$(shell find . -name "*.go")
+
+ifeq (, $(shell which golangci-lint))
+$(warning "could not find golangci-lint in $(PATH), run: curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh")
+endif
+
+.PHONY: fmt lint test install_deps clean
+
+default: all
+
+all: fmt test
+
+fmt:
+	$(info ******************** checking formatting ********************)
+	@test -z $(shell gofmt -l $(SRC)) || (gofmt -d $(SRC); exit 1)
+
+lint:
+	$(info ******************** running lint tools ********************)
+	golangci-lint run -v
+
+test: install_deps
+	$(info ******************** running tests ********************)
+	go test -v ./...
+
+richtest: install_deps
+	$(info ******************** running tests with kyoh86/richgo ********************)
+	richgo test -v ./...
+
+install_deps:
+	$(info ******************** downloading dependencies ********************)
+	go get -v ./...
+
+clean:
+	rm -rf $(BIN)