Refactor app architecture and clean local artifacts

frontend/src/lib/http.ts

@@ -0,0 +1,69 @@
+const API_URL = (import.meta.env.VITE_API_URL ?? '').replace(/\/$/, '')
+const API_LABEL = API_URL || 'same-origin /api'
+export const AUTH_TOKEN_KEY = 'vtsa-session-token'
+
+export class ApiRequestError extends Error {
+  status: number | null
+
+  constructor(message: string, status: number | null = null) {
+    super(message)
+    this.name = 'ApiRequestError'
+    this.status = status
+  }
+}
+
+function getAuthToken() {
+  if (typeof window === 'undefined') return null
+  return window.localStorage.getItem(AUTH_TOKEN_KEY)
+}
+
+function clearAuthToken() {
+  if (typeof window === 'undefined') return
+  window.localStorage.removeItem(AUTH_TOKEN_KEY)
+}
+
+async function parseError(response: Response, path: string) {
+  const error = await response.text().catch(() => '')
+  const message = extractErrorMessage(error) || `API request failed for ${path}`
+  throw new ApiRequestError(message, response.status)
+}
+
+function extractErrorMessage(error: string) {
+  if (!error.trim()) return ''
+
+  try {
+    const parsed = JSON.parse(error) as { message?: unknown; title?: unknown; detail?: unknown }
+    const message = parsed.message ?? parsed.detail ?? parsed.title
+    return typeof message === 'string' ? message : error
+  } catch {
+    return error
+  }
+}
+
+export async function requestJson<TResponse>(
+  path: string,
+  options: RequestInit = {},
+): Promise<TResponse> {
+  const token = getAuthToken()
+  const headers = new Headers(options.headers)
+
+  if (token) {
+    headers.set('Authorization', `Bearer ${token}`)
+  }
+
+  const response = await fetch(`${API_URL}${path}`, {
+    ...options,
+    headers,
+  }).catch(() => {
+    throw new ApiRequestError(`API nicht erreichbar (${API_LABEL}). Bitte Backend starten.`)
+  })
+
+  if (!response.ok) {
+    if (response.status === 401 || response.status === 403) {
+      clearAuthToken()
+    }
+    await parseError(response, path)
+  }
+
+  return response.json() as Promise<TResponse>
+}