monitor_server app

```python
import sqlite3
from fastapi import FastAPI
from fastapi.responses import HTMLResponse
from pydantic import BaseModel


app = FastAPI()

DB_FILE = "db.sqlite"


class ServerData(BaseModel):
    timestamp: int
    static_hostname: str
    machine_id: str
    operating_system: str
    uptime: str
    used_disk: str


def init_db():
    conn = sqlite3.connect(DB_FILE)
    cursor = conn.cursor()

    cursor.execute("""
        CREATE TABLE IF NOT EXISTS servers (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            timestamp INTEGER,
            static_hostname TEXT,
            machine_id TEXT UNIQUE,
            operating_system TEXT,
            uptime TEXT,
            used_disk TEXT
        )
    """)

    conn.commit()
    conn.close()


@app.on_event("startup")
def startup():
    init_db()


@app.get("/", response_class=HTMLResponse)
def root():
    conn = sqlite3.connect(DB_FILE)
    cursor = conn.cursor()

    cursor.execute("""
        SELECT
            id,
            timestamp,
            static_hostname,
            machine_id,
            operating_system,
            uptime,
            used_disk
        FROM servers
    """)

    rows = cursor.fetchall()

    conn.close()

    html = "<h1>Servers List</h1><table border='1'>"
    html += """
        <tr>
            <th>id</th>
            <th>timestamp</th>
            <th>static_hostname</th>
            <th>machine_id</th>
            <th>operating_system</th>
            <th>uptime</th>
            <th>used_disk</th>
        </tr>
    """

    for row in rows:
        html += "<tr>" + "".join(f"<td>{col}</td>" for col in row) + "</tr>"

    html += "</table>"

    return html


@app.post("/servers")
def save_server(server: ServerData):
    conn = sqlite3.connect(DB_FILE)
    cursor = conn.cursor()

    cursor.execute("""
        INSERT INTO servers (
            timestamp,
            static_hostname,
            machine_id,
            operating_system,
            uptime,
            used_disk
        ) VALUES (?, ?, ?, ?, ?, ?)
        ON CONFLICT(machine_id) DO UPDATE SET
            timestamp = excluded.timestamp,
            static_hostname = excluded.static_hostname,
            operating_system = excluded.operating_system,
            uptime = excluded.uptime,
            used_disk = excluded.used_disk
    """, (
        server.timestamp,
        server.static_hostname,
        server.machine_id,
        server.operating_system,
        server.uptime,
        server.used_disk
    ))

    conn.commit()
    conn.close()

    return {"message": "saved"}
```