chore: 将后端移动到 api/ 目录，准备合并为单仓库

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/prompt/schemas.py

@@ -0,0 +1,52 @@
+from typing import Optional
+from uuid import UUID
+from ninja import Schema
+
+
+class MessageOut(Schema):
+    id: int
+    role: str
+    source: str
+    content: str
+    code_html: Optional[str] = None
+    code_css: Optional[str] = None
+    code_js: Optional[str] = None
+    prompt_level: Optional[int] = None
+    created: str
+
+
+class PromptHistoryItemOut(Schema):
+    user_message_id: int
+    assistant_message_id: int
+    submission_id: Optional[UUID] = None
+    source: str
+    prompt: str
+    prompt_level: Optional[int] = None
+    code_html: Optional[str] = None
+    code_css: Optional[str] = None
+    code_js: Optional[str] = None
+    created: str
+
+
+class ConversationOut(Schema):
+    id: UUID
+    user_id: int
+    username: str
+    task_id: int
+    task_title: str
+    is_active: bool
+    message_count: int
+    created: str
+
+    @staticmethod
+    def from_conv(conv):
+        return {
+            "id": conv.id,
+            "user_id": conv.user_id,
+            "username": conv.user.username,
+            "task_id": conv.task_id,
+            "task_title": conv.task.title,
+            "is_active": conv.is_active,
+            "message_count": conv.msg_count if hasattr(conv, "msg_count") else conv.messages.count(),
+            "created": conv.created.isoformat(),
+        }