feat(server): scenario mapping (#13404)

fix AI-404

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

* **New Features**
* Introduced scenario-based configuration for copilot, allowing default
model assignments for various AI use cases.
  * Added a new image generation model to the available options.

* **Improvements**
* Refined copilot provider settings by removing deprecated fallback
options and standardizing base URL configuration.
* Enhanced prompt management to support scenario-driven updates and
improved configuration handling.
* Updated admin and settings interfaces to support new scenario
configurations.

* **Bug Fixes**
* Removed deprecated or unused prompts and related references across
platforms for consistency.

* **Other**
* Improved test coverage and updated test assets to reflect prompt and
scenario changes.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/blocksuite/ai/provider/prompt.ts

@@ -3,7 +3,6 @@
 export const promptKeys = [
   // text actions
   'Chat With AFFiNE AI',
-  'Search With AFFiNE AI',
   'Summary',
   'Summary as title',
   'Generate a caption',