feat(terminus): add method for dynamic module configuration

[mag123c]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/terminus/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

Currently, TerminusModule only supports static configuration through the forRoot() method. This prevents users from dynamically injecting configuration from services like ConfigService or using environment variables at runtime.

Issue Number: #2649

What is the new behavior?

This PR adds forRootAsync() method to TerminusModule that enables dynamic configuration injection. Users can now:

• Use useFactory to dynamically create configuration with dependency injection
• Use useClass to provide a configuration factory class
• Use useExisting to reuse an existing configuration factory provider

Example usage:

TerminusModule.forRootAsync({
  imports: [ConfigModule],
  inject: [ConfigService],
  useFactory: (configService: ConfigService) => ({
    gracefulShutdownTimeoutMs: configService.get('TERMINUS_SHUTDOWN_TIMEOUT', 5000),
    errorLogStyle: configService.get('TERMINUS_LOG_STYLE', 'json'),
    logger: configService.get('TERMINUS_LOGGER_ENABLED', true),
  }),
})

Does this PR introduce a breaking change?

• Yes
• No

Other information

I have a sample application ready that demonstrates the forRootAsync usage with ConfigModule and environment variables. Should I include it as sample/013-forrootasync-app (similar to other sample apps in the repository)?

The sample would show:

• Integration with @nestjs/config
• Environment-based configuration
• All three patterns (useFactory, useClass, useExisting)

Let me know if you'd like me to add it to this PR or keep the PR focused on the core implementation only.

[mag123c]

ci e2e fail reason: #2672