🔧 feat: add OpenTelemetry instrumentation to persistence layer

- Added persistence telemetry configuration option (telemetry.persistence.enabled)
- Created PersistenceTelemetryConfig struct for fine-grained control
- Added GetPersistenceTelemetryEnabled() helper method
- Implemented telemetry span creation in SQLite repository
- Added OpenTelemetry instrumentation to key repository methods:
  - CreateUser: Tracks user creation with error recording
  - GetUserByUsername: Tracks queries with username attribute
- Maintained backward compatibility - telemetry is optional and disabled by default
- Updated all tests to pass config parameter to repository constructor
- Added proper error recording and span attributes for observability

Benefits:
- Performance monitoring of database operations
- Flamegraph generation capability for persistence layer
- Distributed tracing across service boundaries
- Configurable instrumentation for production vs development

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

pkg/user/user_test.go

@@ -6,17 +6,31 @@ import (
 	"testing"
 	"time"
 
+	"dance-lessons-coach/pkg/config"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
+// createTestConfig creates a test configuration with telemetry disabled
+func createTestConfig() *config.Config {
+	return &config.Config{
+		Telemetry: config.TelemetryConfig{
+			Enabled: false,
+			Persistence: config.PersistenceTelemetryConfig{
+				Enabled: false,
+			},
+		},
+	}
+}
+
 func TestSQLiteRepository(t *testing.T) {
 	t.Run("CRUD operations", func(t *testing.T) {
 		// Create a temporary database
 		dbPath := "test_db.sqlite"
 		defer os.Remove(dbPath)
 
-		repo, err := NewSQLiteRepository(dbPath)
+		cfg := createTestConfig()
+		repo, err := NewSQLiteRepository(dbPath, cfg)
 		require.NoError(t, err)
 		defer repo.Close()
 
@@ -92,7 +106,8 @@ func TestAuthService(t *testing.T) {
 		dbPath := "test_auth_db.sqlite"
 		defer os.Remove(dbPath)
 
-		repo, err := NewSQLiteRepository(dbPath)
+		cfg := createTestConfig()
+		repo, err := NewSQLiteRepository(dbPath, cfg)
 		require.NoError(t, err)
 		defer repo.Close()
 
@@ -162,7 +177,8 @@ func TestPasswordResetService(t *testing.T) {
 		dbPath := "test_reset_db.sqlite"
 		defer os.Remove(dbPath)
 
-		repo, err := NewSQLiteRepository(dbPath)
+		cfg := createTestConfig()
+		repo, err := NewSQLiteRepository(dbPath, cfg)
 		require.NoError(t, err)
 		defer repo.Close()