feat: 紫微·磁场管理打卡系统

- Flomo 风格左右布局（侧边栏+主内容区）
- 日历导航：月视图，三色状态圆点，点击日期快速切换
- 四层修为：立志/责善/改过/勤学
- 勤学 8 个固定预设项目，勾选后显示备注
- 编辑后 1.5 秒自动保存，切换日期静默保存
- Flask + SQLite，端口 5056

database.py

@@ -0,0 +1,94 @@
+# -*- coding: utf-8 -*-
+"""ziwei-power SQLite 数据库操作层"""
+
+import sqlite3
+import json
+import os
+from datetime import datetime
+
+DB_DIR = os.path.join(os.path.expanduser('~'), '.workbuddy', 'data', 'ziwei-power')
+os.makedirs(DB_DIR, exist_ok=True)
+DB_PATH = os.path.join(DB_DIR, 'ziwei_power.db')
+
+
+def get_conn():
+    conn = sqlite3.connect(DB_PATH)
+    conn.row_factory = sqlite3.Row
+    return conn
+
+
+def init_db():
+    """初始化数据库表"""
+    conn = get_conn()
+    conn.execute('''
+        CREATE TABLE IF NOT EXISTS checkins (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            date TEXT UNIQUE NOT NULL,
+            data TEXT NOT NULL,
+            created_at TEXT NOT NULL,
+            updated_at TEXT NOT NULL
+        )
+    ''')
+    conn.commit()
+    conn.close()
+
+
+def get_checkin(date_str):
+    """获取某天的打卡记录，返回 dict 或 None"""
+    conn = get_conn()
+    row = conn.execute('SELECT * FROM checkins WHERE date = ?', (date_str,)).fetchone()
+    conn.close()
+    if row:
+        return {
+            'id': row['id'],
+            'date': row['date'],
+            'data': json.loads(row['data']),
+            'created_at': row['created_at'],
+            'updated_at': row['updated_at']
+        }
+    return None
+
+
+def save_checkin(date_str, data_dict):
+    """保存或更新打卡记录"""
+    now = datetime.now().isoformat()
+    conn = get_conn()
+    existing = conn.execute('SELECT id FROM checkins WHERE date = ?', (date_str,)).fetchone()
+    json_data = json.dumps(data_dict, ensure_ascii=False)
+    if existing:
+        conn.execute(
+            'UPDATE checkins SET data = ?, updated_at = ? WHERE date = ?',
+            (json_data, now, date_str)
+        )
+    else:
+        conn.execute(
+            'INSERT INTO checkins (date, data, created_at, updated_at) VALUES (?, ?, ?, ?)',
+            (date_str, json_data, now, now)
+        )
+    conn.commit()
+    conn.close()
+
+
+def delete_checkin(date_str):
+    """删除某天的打卡记录"""
+    conn = get_conn()
+    conn.execute('DELETE FROM checkins WHERE date = ?', (date_str,))
+    conn.commit()
+    conn.close()
+
+
+def get_all_checkins():
+    """获取所有打卡记录，按日期倒序"""
+    conn = get_conn()
+    rows = conn.execute('SELECT * FROM checkins ORDER BY date DESC').fetchall()
+    conn.close()
+    results = []
+    for row in rows:
+        results.append({
+            'id': row['id'],
+            'date': row['date'],
+            'data': json.loads(row['data']),
+            'created_at': row['created_at'],
+            'updated_at': row['updated_at']
+        })
+    return results