Add FastAPI backend with agent system

backend/app/schemas/forum.py

@@ -0,0 +1,37 @@
+from pydantic import BaseModel
+
+
+class ForumPostCreate(BaseModel):
+    title: str
+    content: str
+    category: str | None = "discussion"
+
+
+class ForumPostOut(BaseModel):
+    id: str
+    user_id: str
+    title: str
+    content: str
+    category: str | None
+    is_executed: bool
+    execution_result: str | None
+    reply_count: int
+    created_at: str
+
+    model_config = {"from_attributes": True}
+
+
+class ForumReplyCreate(BaseModel):
+    content: str
+
+
+class ForumReplyOut(BaseModel):
+    id: str
+    post_id: str
+    user_id: str | None
+    agent_id: str | None
+    content: str
+    is_ai_reply: bool
+    created_at: str
+
+    model_config = {"from_attributes": True}