prepare fastapi root layout for server deployment

app/api/agent.py

@@ -0,0 +1,31 @@
+from fastapi import APIRouter, Depends
+from sqlalchemy.orm import Session
+
+from app.core.config import settings
+from app.core.response import ApiResponse, ok
+from app.core.user_context import UserContext, get_user_context
+from app.db.session import get_db
+from app.schemas.agent import AgentHelloResponse, AgentHelloUser
+from app.services.audit_service import AuditService
+
+router = APIRouter()
+
+
+@router.get("/agent/hello", response_model=ApiResponse[AgentHelloResponse])
+def hello(ctx: UserContext = Depends(get_user_context), db: Session = Depends(get_db)):
+    """Agent Hello：读取宿主用户上下文并返回 Demo 功能配置。"""
+    AuditService(db).log(ctx, "agent.hello", "agent")
+    db.commit()
+    return ok(
+        AgentHelloResponse(
+            user=AgentHelloUser(
+                user_id=ctx.user_id,
+                tenant_id=ctx.tenant_id,
+                role=ctx.role,
+                source=ctx.auth_source,
+                username=ctx.username,
+                display_name=ctx.display_name,
+            ),
+            features=settings.as_public_dict(),
+        )
+    )