feat: initial frontend - React + TypeScript + Vite

- Login page with JWT auth
- Dashboard with stats and charts
- Issues list with pagination, filtering
- Issue detail with comments, status transitions
- Create issue form
- Dark theme UI
- Docker (nginx) with API proxy to backend
- Sidebar navigation

src/hooks/useAuth.ts

@@ -0,0 +1,51 @@
+import { useState, useEffect, useCallback } from 'react'
+import api from '@/services/api'
+import type { User } from '@/types'
+
+interface AuthState {
+  user: User | null
+  token: string | null
+  loading: boolean
+}
+
+export function useAuth() {
+  const [state, setState] = useState<AuthState>({
+    user: null,
+    token: localStorage.getItem('token'),
+    loading: true,
+  })
+
+  const fetchUser = useCallback(async () => {
+    const token = localStorage.getItem('token')
+    if (!token) {
+      setState({ user: null, token: null, loading: false })
+      return
+    }
+    try {
+      const { data } = await api.get<User>('/auth/me')
+      setState({ user: data, token, loading: false })
+    } catch {
+      localStorage.removeItem('token')
+      setState({ user: null, token: null, loading: false })
+    }
+  }, [])
+
+  useEffect(() => { fetchUser() }, [fetchUser])
+
+  const login = async (username: string, password: string) => {
+    const form = new URLSearchParams()
+    form.append('username', username)
+    form.append('password', password)
+    const { data } = await api.post('/auth/login', form)
+    localStorage.setItem('token', data.access_token)
+    setState((s) => ({ ...s, token: data.access_token }))
+    await fetchUser()
+  }
+
+  const logout = () => {
+    localStorage.removeItem('token')
+    setState({ user: null, token: null, loading: false })
+  }
+
+  return { ...state, login, logout }
+}