feat: add frontend auth shell

frontend/src/features/auth/AuthProvider.tsx

@@ -0,0 +1,92 @@
+import * as React from 'react'
+
+import * as authApi from './api'
+import type { CurrentUser } from './types'
+
+type AuthContextValue = {
+  user: CurrentUser | null
+  loading: boolean
+  authenticated: boolean
+  login: (username: string, password: string) => Promise<void>
+  logout: () => Promise<void>
+  refresh: () => Promise<void>
+}
+
+const AuthContext = React.createContext<AuthContextValue | null>(null)
+
+type AuthProviderProps = {
+  children: React.ReactNode
+}
+
+export function AuthProvider({ children }: AuthProviderProps) {
+  const [user, setUser] = React.useState<CurrentUser | null>(null)
+  const [loading, setLoading] = React.useState(true)
+
+  const refresh = React.useCallback(async () => {
+    try {
+      const currentUser = await authApi.getCurrentUser()
+      setUser(currentUser)
+    } catch {
+      setUser(null)
+    }
+  }, [])
+
+  React.useEffect(() => {
+    let mounted = true
+
+    authApi
+      .getCurrentUser()
+      .then((currentUser) => {
+        if (mounted) {
+          setUser(currentUser)
+        }
+      })
+      .catch(() => {
+        if (mounted) {
+          setUser(null)
+        }
+      })
+      .finally(() => {
+        if (mounted) {
+          setLoading(false)
+        }
+      })
+
+    return () => {
+      mounted = false
+    }
+  }, [])
+
+  const handleLogin = React.useCallback(async (username: string, password: string) => {
+    const currentUser = await authApi.login(username, password)
+    setUser(currentUser)
+  }, [])
+
+  const handleLogout = React.useCallback(async () => {
+    await authApi.logout()
+    setUser(null)
+    window.location.hash = '/'
+  }, [])
+
+  const value = React.useMemo<AuthContextValue>(
+    () => ({
+      user,
+      loading,
+      authenticated: Boolean(user),
+      login: handleLogin,
+      logout: handleLogout,
+      refresh
+    }),
+    [handleLogin, handleLogout, loading, refresh, user]
+  )
+
+  return <AuthContext.Provider value={value}>{children}</AuthContext.Provider>
+}
+
+export function useAuth() {
+  const context = React.useContext(AuthContext)
+  if (!context) {
+    throw new Error('useAuth must be used within AuthProvider')
+  }
+  return context
+}