init: 从 /root/zikai 根目录迁入

把原本散落在 /root/zikai 的 FastAPI 服务整理到 server/ 子目录，
开启独立 git 与 venv。运行时数据（config.yaml / keys / uploads）
按 .gitignore 留在工作目录但不入仓。

app/schemas/system.py

@@ -0,0 +1,31 @@
+"""系统状态接口 DTO。"""
+
+from __future__ import annotations
+
+from pydantic import BaseModel, Field
+
+
+class MemoryUsage(BaseModel):
+    total: int = Field(..., description="物理内存总量（字节）")
+    available: int = Field(..., description="可用内存（字节）")
+    used: int = Field(..., description="已用内存（字节）")
+    percent: float = Field(..., description="使用率 0-100")
+
+
+class DiskUsage(BaseModel):
+    device: str
+    mountpoint: str
+    fstype: str
+    total: int
+    used: int
+    free: int
+    percent: float
+
+
+class SystemStatus(BaseModel):
+    hostname: str
+    cpu_percent: float = Field(..., description="CPU 使用率（所有核平均）")
+    cpu_count: int
+    memory: MemoryUsage
+    disks: list[DiskUsage]
+    uptime_seconds: float