feat: multi-user auth with role-based access

- Server checks PIN against env (super admin) + NocoDB Users table
- Session stores name + role (admin/viewer)
- Admin: sees Settings page (seasons + users management)
- Viewer: sees Dashboard + Comparison only, no Settings
- Users CRUD on Settings page: add name + PIN + role, delete
- Settings link + nav hidden for non-admin users

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/Login.tsx

@@ -2,7 +2,7 @@ import React, { useState } from 'react';
 import { useLanguage } from '../contexts/LanguageContext';
 
 interface LoginProps {
-  onLogin: () => void;
+  onLogin: (name: string, role: string) => void;
 }
 
 function Login({ onLogin }: LoginProps) {
@@ -30,7 +30,8 @@ function Login({ onLogin }: LoginProps) {
         return;
       }
 
-      onLogin();
+      const data = await res.json();
+      onLogin(data.name || '', data.role || 'viewer');
     } catch {
       setError(t('login.error'));
       setLoading(false);