feat: integra /sistema/usuarios e /sistema/configuracoes com API real

- useApi.ts: composable centralizado com Authorization header automático
- usuarios.vue: GET /api/v1/users — lista usuários reais do tenant
- configuracoes.vue: GET/PUT /api/v1/tenant/me — carrega e salva dados reais

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

front-end/app/composables/useApi.ts

@@ -0,0 +1,17 @@
+// Wrapper sobre $fetch que injeta o Authorization header automaticamente.
+export function useApi() {
+  const { public: { apiBase } } = useRuntimeConfig()
+  const token = useCookie<string | null>('auth_token')
+
+  function apiFetch<T>(path: string, options: Parameters<typeof $fetch>[1] = {}): Promise<T> {
+    return $fetch<T>(`${apiBase}${path}`, {
+      ...options,
+      headers: {
+        ...(options.headers as Record<string, string> || {}),
+        ...(token.value ? { Authorization: `Bearer ${token.value}` } : {}),
+      },
+    })
+  }
+
+  return { apiFetch }
+}