Backend Complete: Interface Refactoring & Service Container Enhancements

Repository Interface Optimization:
- Created IBaseRepository.ts and IPaginatedRepository.ts
- Refactored all 7 repository interfaces to extend base interfaces
- Eliminated ~200 lines of redundant code (70% reduction)
- Improved type safety and maintainability

 Dependency Injection Improvements:
- Added EmailService and GameTokenService to DIContainer
- Updated CreateUserCommandHandler constructor for DI
- Updated RequestPasswordResetCommandHandler constructor for DI
- Enhanced testability and service consistency

 Environment Configuration:
- Created comprehensive .env.example with 40+ variables
- Organized into 12 logical sections (Database, Security, Email, etc.)
- Added security guidelines and best practices
- Documented all backend environment requirements

 Documentation:
- Added comprehensive codebase review
- Created refactoring summary report
- Added frontend implementation guide

Impact: Improved code quality, reduced maintenance overhead, enhanced developer experience

SerpentRace_Backend/src/Application/Game/commands/JoinGameCommand.ts

@@ -0,0 +1,9 @@
+import { LoginType } from '../../../Domain/Game/GameAggregate';
+
+export interface JoinGameCommand {
+  gameCode: string;  // 6-character game code
+  playerId?: string;  // User ID of the player joining (optional for public games)
+  playerName?: string;  // Display name for the player (required for public games)
+  orgId?: string | null;  // Organization ID (for organization games)
+  loginType: LoginType;  // Type of join being attempted
+}