feat: Replace string with typed unions for aspectRatio in image/video configs

[puretension]

Summary

Improves type safety for aspectRatio parameters across media generation APIs by replacing loose string types with strongly-typed unions.

Changes

• Add ImageAspectRatio and VideoAspectRatio type definitions
• Update GenerateImagesConfig, EditImageConfig, and GenerateVideosConfig interfaces
• Enable IDE autocomplete and compile-time validation

🚀 Developer Experience Improvement

Before	After
❌ No type safety or autocomplete	✅ Full type safety with autocomplete
No guidance for developers	Perfect IDE autocomplete support

Benefits

• Better developer experience with autocomplete
• Prevents invalid aspect ratio values at compile time
• Centralizes aspect ratio definitions (DRY principle)
• Maintains 100% backward compatibility

Type Definitions

// Common aspect ratios supported across all media generation APIs
export type CommonAspectRatio = "9:16" | "16:9";

// Aspect ratios for image generation and editing
export type ImageAspectRatio = CommonAspectRatio | "1:1" | "3:4" | "4:3";

// Aspect ratios for video generation  
export type VideoAspectRatio = CommonAspectRatio;

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[shmishra99]

Hi @puretension,

Thanks for your contribution to the SDK. We've noticed your forked repository currently has a merge conflict. Could you please resolve the conflict on your end so we can proceed with reviewing the PR? We appreciate your work.

[puretension]

Hi @shmishra99,

Thank you for the feedback! I've resolved the merge conflict on my end. The PR should now be ready for review.

I really appreciate you taking the time to look at this contribution and have been looking forward to your feedback.
Please let me know if there's any additional feedback or if there are any other changes needed from my side.