feat(core): move context docs to user prompt (#10162)

Fix issue [BS-2522](https://linear.app/affine-design/issue/BS-2522).

### Why make this change?
If the user data contains illegal content, carrying the user data in the system prompt will run the risk of having the account banned.

### What Changed?
- Move the `Context Documents` to the user prompt.
- Add `withPrompt` in `QueryChatHistoriesInput` options.
- Get chat histories without prompt messages.
- Omit document context when saving messages to the `aiSessionMessage` db.

packages/backend/server/src/plugins/copilot/resolver.ts

@@ -151,6 +151,9 @@ class QueryChatHistoriesInput implements Partial<ListHistoriesOptions> {
 
   @Field(() => String, { nullable: true })
   sessionId: string | undefined;
+
+  @Field(() => Boolean, { nullable: true })
+  withPrompt: boolean | undefined;
 }
 
 // ================== Return Types ==================
@@ -346,8 +349,7 @@ export class CopilotResolver {
       user.id,
       workspaceId,
       docId,
-      options,
-      true
+      options
     );
 
     return histories.map(h => ({