feat(auth): add email/password login restricted to @craze.de accounts

- src/lib/auth.ts: signIn/signOut/getStoredSession via Supabase Auth REST API
- src/components/LoginPage.tsx: login form with domain validation UI
- src/components/TopBar.tsx: show logged-in user email + sign out button
- src/App.tsx: gate entire app behind auth — shows LoginPage if no session

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

src/components/TopBar.tsx

@@ -1,14 +1,16 @@
 import React from 'react';
-import { Download, Database } from 'lucide-react';
+import { Download, Database, LogOut } from 'lucide-react';
 
 interface TopBarProps {
   stats: any;
   onExport: () => void;
   hasData: boolean;
   hasUnsavedChanges: boolean;
+  userEmail?: string;
+  onSignOut?: () => void;
 }
 
-export function TopBar({ stats, onExport, hasData, hasUnsavedChanges }: TopBarProps) {
+export function TopBar({ stats, onExport, hasData, hasUnsavedChanges, userEmail, onSignOut }: TopBarProps) {
   return (
     <header className="bg-slate-800 border-b border-slate-700 h-16 flex items-center justify-between px-6 shrink-0 z-10">
       <div className="flex items-center gap-3">
@@ -50,8 +52,8 @@ export function TopBar({ stats, onExport, hasData, hasUnsavedChanges }: TopBarPr
           <button
             onClick={onExport}
             className={`flex items-center gap-2 px-4 py-2 rounded-md text-sm font-medium transition-colors ${
-              hasUnsavedChanges 
-                ? 'bg-blue-600 hover:bg-blue-700 text-white' 
+              hasUnsavedChanges
+                ? 'bg-blue-600 hover:bg-blue-700 text-white'
                 : 'bg-slate-700 hover:bg-slate-600 text-slate-200'
             }`}
           >
@@ -60,6 +62,18 @@ export function TopBar({ stats, onExport, hasData, hasUnsavedChanges }: TopBarPr
             {hasUnsavedChanges && <span className="w-2 h-2 rounded-full bg-red-500 ml-1 animate-pulse" />}
           </button>
         )}
+        {userEmail && (
+          <div className="flex items-center gap-2 border-l border-slate-700 pl-3">
+            <span className="text-xs text-slate-400">{userEmail}</span>
+            <button
+              onClick={onSignOut}
+              title="Sign out"
+              className="p-1.5 text-slate-400 hover:text-white hover:bg-slate-700 rounded-md transition-colors"
+            >
+              <LogOut className="w-4 h-4" />
+            </button>
+          </div>
+        )}
       </div>
     </header>
   );