feat: 初始化义工时长管理系统

- 管理台：活动设置、时长登记、用户管理、数据导出（Excel/PNG）
- 用户端：姓名查询个人义工时长与活动记录
- 技术栈：React + Vite + TailwindCSS / Node.js + Express + sql.js (SQLite)
- 支持 Docker 部署，附带 Gitea Actions 自动部署工作流
- 响应式界面，兼容移动端与 PC 端
- 默认管理员账号：admin / admin123

server/src/db/schema.sql

@@ -0,0 +1,50 @@
+CREATE TABLE IF NOT EXISTS work_groups (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  name TEXT NOT NULL UNIQUE
+);
+
+CREATE TABLE IF NOT EXISTS users (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  class TEXT NOT NULL,
+  name TEXT NOT NULL,
+  volunteer_no TEXT,
+  group_id INTEGER,
+  FOREIGN KEY (group_id) REFERENCES work_groups(id) ON DELETE SET NULL,
+  UNIQUE(class, name)
+);
+
+CREATE TABLE IF NOT EXISTS activities (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  title TEXT NOT NULL,
+  content TEXT,
+  start_time TEXT NOT NULL,
+  end_time TEXT NOT NULL,
+  created_at TEXT NOT NULL DEFAULT (datetime('now','localtime'))
+);
+
+CREATE TABLE IF NOT EXISTS activity_groups (
+  activity_id INTEGER NOT NULL,
+  group_id INTEGER NOT NULL,
+  PRIMARY KEY (activity_id, group_id),
+  FOREIGN KEY (activity_id) REFERENCES activities(id) ON DELETE CASCADE,
+  FOREIGN KEY (group_id) REFERENCES work_groups(id) ON DELETE CASCADE
+);
+
+CREATE TABLE IF NOT EXISTS hours (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  activity_id INTEGER NOT NULL,
+  user_id INTEGER NOT NULL,
+  hours REAL NOT NULL DEFAULT 0,
+  remark TEXT,
+  created_at TEXT NOT NULL DEFAULT (datetime('now','localtime')),
+  FOREIGN KEY (activity_id) REFERENCES activities(id) ON DELETE CASCADE,
+  FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE,
+  UNIQUE(activity_id, user_id)
+);
+
+CREATE TABLE IF NOT EXISTS admins (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  username TEXT NOT NULL UNIQUE,
+  password_hash TEXT NOT NULL,
+  created_at TEXT NOT NULL DEFAULT (datetime('now','localtime'))
+);