move dynamic module composition behind typed environment config

[Emoji-dot]

close #336
What Was Changed

1. Created EnvironmentModuleLoader Class
   File: app/backend/src/module-factory.ts

Class-based encapsulation replacing the standalone function approach
Three public methods:
getModules() - Returns dynamic modules based on feature flags (ReconciliationModule, NotificationsModule, DeveloperModule)
getProviders() - Returns conditional providers (IngestionBootstrapService when INGESTION_ENABLED)
getConfig() - Exposes the validated environment configuration
Private validation method:
validateConfiguration() - Runs production safety checks (blocks DeveloperModule in production)
Backward compatibility: Kept getDynamicModules() function as a deprecated wrapper
2. Refactored app.module.ts
File: app/backend/src/app.module.ts

Before:

typescript

const validatedEnv = envSchema.validate(...).value as EnvConfig;

@module({
imports: [
...getDynamicModules(validatedEnv),
],
providers: [
...(validatedEnv.INGESTION_ENABLED ? [IngestionBootstrapService] : []),
],
})
After:

typescript

const validatedEnv = envSchema.validate(...).value as EnvConfig;
const moduleLoader = new EnvironmentModuleLoader(validatedEnv);

@module({
imports: [
...moduleLoader.getModules(),
],
providers: [
...moduleLoader.getProviders(),
],
})
Changes:

Replaced getDynamicModules(validatedEnv) with moduleLoader.getModules()
Replaced inline ternary INGESTION_ENABLED check with moduleLoader.getProviders()
Removed unused IngestionBootstrapService import (now handled internally by loader)
3. Comprehensive Test Coverage
File: app/backend/src/module-factory.unit.spec.ts (19 tests)

Tests for EnvironmentModuleLoader class:

✅ getModules() with various feature flag combinations (6 tests)
✅ getProviders() for ingestion service registration (3 tests)
✅ getConfig() returns validated config (1 test)
✅ Constructor validation for production safety (3 tests)
✅ Backward compatibility for deprecated getDynamicModules() (6 tests)
File: app/backend/src/app.module.unit.spec.ts (10 tests)

Integration tests for AppModule:

✅ Module compilation with different feature flag configurations (6 tests)
✅ Production safety checks (2 tests)
✅ Environment configuration integration (2 tests)
4. Test Execution Results
Cleaned up 318 stray .js files from src/ directory that were causing test failures
All 29 tests passing:
module-factory.unit.spec.ts: 19/19 ✅
app.module.unit.spec.ts: 10/10 ✅
Benefits of the Refactoring
Better Encapsulation - Logic is grouped in a cohesive class instead of scattered functions
Type Safety - All methods have explicit return types and typed parameters
Improved Testability - Easier to test module composition in isolation
Maintainability - Clear separation of concerns (validation, module loading, provider registration)
Runtime Safety - Production checks happen at instantiation time, failing fast
Extensibility - Easy to add new conditional modules or providers in the future
Backward Compatibility - Existing code using getDynamicModules() still works
Files Modified
✅ app/backend/src/module-factory.ts - Created EnvironmentModuleLoader class
✅ app/backend/src/app.module.ts - Updated to use the new loader
✅ app/backend/src/module-factory.unit.spec.ts - Comprehensive unit tests
✅ app/backend/src/app.module.unit.spec.ts - Integration tests