feat(server): switch i2i to gpt (#12238)

fix AI-14
fix AI-17
fix AI-39
fix AI-112

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - Expanded and reorganized prompt options for text and image actions, adding new prompts for image generation, style conversions, upscaling, background removal, and sticker creation.
  - Enhanced image editing capabilities with direct support for image attachments in prompts.

- **Improvements**
  - Updated prompt names and descriptions to be more user-friendly and descriptive.
  - Simplified and clarified prompt selection and image processing workflows with improved default behaviors.
  - Better organization of prompts through clear grouping and categorization.

- **Bug Fixes**
  - Improved validation and handling of image attachments during editing requests.

- **Refactor**
  - Internal code restructuring of prompts and provider logic for clarity and maintainability without affecting user workflows.
  - Refined message handling and content merging logic to ensure consistent prompt processing.
  - Adjusted image attachment rendering logic for improved display consistency.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/copilot/providers/utils.ts

@@ -39,7 +39,7 @@ const FORMAT_INFER_MAP: Record<string, string> = {
   flv: 'video/flv',
 };
 
-async function inferMimeType(url: string) {
+export async function inferMimeType(url: string) {
   if (url.startsWith('data:')) {
     return url.split(';')[0].split(':')[1];
   }