feat: 首页仪表盘改造为深色科技风格 + Apple Health 步数同步

UI 改造:
- 首页采用深色科技风格 (Dark Tech)
- Tailwind CSS + Glass Morphism 毛玻璃效果
- 左侧边栏导航 (PC端) / 底部导航 (移动端)
- Material Symbols 图标 + Space Grotesk 字体
- Chart.js 深色主题适配

新功能:
- Apple Health 步数同步 API (/api/steps)
- 设置页面添加 iOS 快捷指令配置说明

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/vitals/core/database.py

@@ -200,6 +200,22 @@ def init_db():
             )
         """)
 
+        # 步数记录表
+        cursor.execute("""
+            CREATE TABLE IF NOT EXISTS steps (
+                id INT PRIMARY KEY AUTO_INCREMENT,
+                user_id INT DEFAULT 1,
+                date DATE NOT NULL,
+                steps INT NOT NULL DEFAULT 0,
+                distance FLOAT,
+                calories INT,
+                source VARCHAR(50) DEFAULT 'apple_health',
+                synced_at DATETIME NOT NULL,
+                UNIQUE KEY unique_user_date (user_id, date),
+                INDEX idx_steps_date (date)
+            )
+        """)
+
         # 创建默认管理员用户（仅在用户表为空时）
         cursor.execute("SELECT COUNT(*) as count FROM users")
         if cursor.fetchone()["count"] == 0:
@@ -277,6 +293,74 @@ def delete_exercise(exercise_id: int):
         cursor.execute("DELETE FROM exercise WHERE id = %s", (exercise_id,))
 
 
+# ===== 步数记录 =====
+
+def add_or_update_steps(user_id: int, record_date: date, steps: int, distance: float = None, calories: int = None, source: str = "apple_health") -> int:
+    """添加或更新步数记录（同一天只保留一条记录）"""
+    with get_connection() as (conn, cursor):
+        cursor.execute("""
+            INSERT INTO steps (user_id, date, steps, distance, calories, source, synced_at)
+            VALUES (%s, %s, %s, %s, %s, %s, %s)
+            ON DUPLICATE KEY UPDATE
+                steps = VALUES(steps),
+                distance = VALUES(distance),
+                calories = VALUES(calories),
+                source = VALUES(source),
+                synced_at = VALUES(synced_at)
+        """, (
+            user_id,
+            record_date.isoformat(),
+            steps,
+            distance,
+            calories,
+            source,
+            datetime.now().isoformat(),
+        ))
+        return cursor.lastrowid
+
+
+def get_steps(start_date: Optional[date] = None, end_date: Optional[date] = None, user_id: Optional[int] = None) -> list[dict]:
+    """查询步数记录"""
+    with get_connection() as (conn, cursor):
+        query = "SELECT * FROM steps WHERE 1=1"
+        params = []
+
+        if user_id:
+            query += " AND user_id = %s"
+            params.append(user_id)
+        if start_date:
+            query += " AND date >= %s"
+            params.append(start_date.isoformat())
+        if end_date:
+            query += " AND date <= %s"
+            params.append(end_date.isoformat())
+
+        query += " ORDER BY date DESC"
+        cursor.execute(query, params)
+
+        return [
+            {
+                "id": row["id"],
+                "date": _parse_date(row["date"]).isoformat() if isinstance(row["date"], str) else row["date"].isoformat(),
+                "steps": row["steps"],
+                "distance": row["distance"],
+                "calories": row["calories"],
+                "source": row["source"],
+                "synced_at": row["synced_at"].isoformat() if row["synced_at"] else None,
+            }
+            for row in cursor.fetchall()
+        ]
+
+
+def get_today_steps(user_id: int) -> dict:
+    """获取今日步数"""
+    today = date.today()
+    records = get_steps(start_date=today, end_date=today, user_id=user_id)
+    if records:
+        return records[0]
+    return {"date": today.isoformat(), "steps": 0, "distance": None, "calories": None}
+
+
 # ===== 饮食记录 =====
 
 def add_meal(meal: Meal, user_id: int = 1) -> int: