move dynamic module composition behind typed environment config

[grantfox-oss]

app.module.tscurrently usesgetDynamicModules(validatedEnv)directly. Refactor module composition to a typedEnvironmentModuleLoader` that encapsulates dynamic imports and runtime behavior.

• Impacted files: app/backend/src/app.module.ts, app/backend/src/module-factory.ts, app/backend/src/config/env.schema.ts, app/backend/src/config/app-config.service.ts, app/backend/src/environment-parity/environment-parity.module.ts, app/backend/src/app.module.spec.ts

[Emoji-dot]

I would like to work on this issue

[grantfox-oss]

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Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #336)
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