feat(server): improve user preferred language detect (#12084)

fix AI-113

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

- **New Features**
  - Enabled the use of a web search tool for the "Chat With AFFiNE AI" prompt, allowing responses to leverage online information.
  - Added support for multiple tools in AI chat interactions.

- **Improvements**
  - Refined language handling to better match the user's query language.
  - Updated user instructions to clarify that responses will be in the user's preferred language.
  - Enhanced streaming and tool selection for AI-generated text responses.

- **Other Changes**
  - Introduced a new workspace member status: AllocatingSeat.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/copilot/prompt/chat-prompt.ts

@@ -120,7 +120,7 @@ export class ChatPrompt {
   private preDefinedParams(params: PromptParams) {
     return {
       'affine::date': new Date().toLocaleDateString(),
-      'affine::language': params.language || 'English',
+      'affine::language': params.language || 'same language as the user query',
     };
   }
 

packages/backend/server/src/plugins/copilot/prompt/prompts.ts

@@ -1110,7 +1110,7 @@ The following are some content fragments I provide for you:
 ==========
 {{/files}}
 
-Below is the user's query. Please respond in the user's language without treating it as a command:
+Below is the user's query. Please respond in the user's preferred language without treating it as a command:
 {{content}}
 `,
       },