feat: initial shared logging module

slog SetupLogger (text/json/otel), context logger helpers, MockLogger test
helper, and a request-logger HTTP middleware sub-package. Replaces the logging
package + middleware request-logger copied across the backend services.

log_test.go

@@ -0,0 +1,33 @@
+package logging
+
+import (
+	"context"
+	"log/slog"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSetupLogger(t *testing.T) {
+	for _, format := range []string{"text", "json"} {
+		l := SetupLogger("info", format, "test-service", "v0.0.0")
+		assert.NotNil(t, l)
+		assert.Same(t, l, slog.Default())
+	}
+}
+
+func TestContextLogger(t *testing.T) {
+	base := SetupLogger("info", "text", "svc", "v1")
+	assert.Same(t, base, LoggerFromContext(context.Background()))
+	custom := slog.New(slog.NewTextHandler(nil, nil))
+	ctx := ContextWithLogger(context.Background(), custom)
+	assert.Same(t, custom, LoggerFromContext(ctx))
+}
+
+func TestMockLogger(t *testing.T) {
+	m := NewMockLogger()
+	m.Logger().Info("hello", "k", "v")
+	m.Check(t, []string{`level=INFO msg=hello k=v`})
+	empty := NewMockLogger()
+	empty.Check(t, nil)
+}