Add full AARS system - Attendance & Accident Record System

- FastAPI backend with SQLite database
- React + TailwindCSS frontend
- JWT authentication
- Excel upload/download for attendance and accident records
- Shift roster management with S7a/S7b split
- Lateness/OT calculation based on shift times
- Roster info API endpoints
- Export API with token query parameter support
- Docker compose deployment

frontend/src/context/AuthContext.jsx

@@ -0,0 +1,52 @@
+import { createContext, useContext, useState, useEffect } from 'react'
+import api from '../api'
+
+const AuthContext = createContext(null)
+
+export function AuthProvider({ children }) {
+  const [user, setUser] = useState(null)
+  const [loading, setLoading] = useState(true)
+
+  useEffect(() => {
+    const token = localStorage.getItem('aars_token')
+    if (token) {
+      api.defaults.headers.common['Authorization'] = `Bearer ${token}`
+      fetchUser()
+    } else {
+      setLoading(false)
+    }
+  }, [])
+
+  const fetchUser = async () => {
+    try {
+      const { data } = await api.get('/api/auth/me')
+      setUser(data)
+    } catch (err) {
+      localStorage.removeItem('aars_token')
+      delete api.defaults.headers.common['Authorization']
+    } finally {
+      setLoading(false)
+    }
+  }
+
+  const login = async (email, password) => {
+    const { data } = await api.post('/api/auth/login', { email, password })
+    localStorage.setItem('aars_token', data.access_token)
+    api.defaults.headers.common['Authorization'] = `Bearer ${data.access_token}`
+    await fetchUser()
+  }
+
+  const logout = () => {
+    localStorage.removeItem('aars_token')
+    delete api.defaults.headers.common['Authorization']
+    setUser(null)
+  }
+
+  return (
+    <AuthContext.Provider value={{ user, loading, login, logout }}>
+      {children}
+    </AuthContext.Provider>
+  )
+}
+
+export const useAuth = () => useContext(AuthContext)