Extract duplicated SimpleEventEmitter class from multiple service files into a shared utility file `js/utils/eventEmitter.js`.
- Created `js/utils/eventEmitter.js` with unified implementation.
- Refactored `AuthService`, `NostrService`, `ModerationService`, and `PlaybackService` to use the shared class.
- Added support for constructor-defined context strings for improved error logging.
- Added comprehensive unit tests for `SimpleEventEmitter`.
- Verified changes with targeted service tests.
Co-authored-by: PR0M3TH3AN <[email protected]>