🔧 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>

cmd/server/main.go

@@ -12,14 +12,14 @@
 //	@license.name	MIT
 //	@license.url	https://opensource.org/licenses/MIT
 
-//	@host		localhost:8080
-//	@BasePath	/api
-//	@schemes	http https
+//	@host						localhost:8080
+//	@BasePath					/api
+//	@schemes					http https
 //
 //	@securityDefinitions.apikey	ApiKeyAuth
-//	@in				header
-//	@name			Authorization
-//	@description	JWT authentication using Bearer token. Format: Bearer <token>
+//	@in							header
+//	@name						Authorization
+//	@description				JWT authentication using Bearer token. Format: Bearer <token>
 
 package main