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.

middleware/request_logger_test.go

@@ -0,0 +1,26 @@
+package middleware
+
+import (
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRequestLogger(t *testing.T) {
+	called := false
+	h := RequestLogger(slog.New(slog.NewTextHandler(nil, nil)))(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		called = true
+		w.WriteHeader(http.StatusCreated)
+		_, _ = w.Write([]byte("ok"))
+	}))
+	req := httptest.NewRequest(http.MethodPost, "/q", strings.NewReader("body"))
+	rw := httptest.NewRecorder()
+	h.ServeHTTP(rw, req)
+	assert.True(t, called)
+	assert.Equal(t, http.StatusCreated, rw.Code)
+	assert.Equal(t, "ok", rw.Body.String())
+}