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/__tests__/mocks/copilot.mock.ts

@@ -84,29 +84,12 @@ export class MockCopilotProvider extends OpenAIProvider {
       ],
     },
     {
-      id: 'lcm-sd15-i2i',
+      id: 'gpt-image-1',
       capabilities: [
         {
-          input: [ModelInputType.Image],
-          output: [ModelOutputType.Image],
-        },
-      ],
-    },
-    {
-      id: 'clarity-upscaler',
-      capabilities: [
-        {
-          input: [ModelInputType.Image],
-          output: [ModelOutputType.Image],
-        },
-      ],
-    },
-    {
-      id: 'imageutils/rembg',
-      capabilities: [
-        {
-          input: [ModelInputType.Image],
+          input: [ModelInputType.Text, ModelInputType.Image],
           output: [ModelOutputType.Image],
+          defaultForOutputType: true,
         },
       ],
     },