Add Mobile Safari optimizations and fixes to signup page

- Implement device detection and performance optimization flags
- Add dynamic CSS classes based on device capabilities
- Create mobile safari utility functions and client plugin
- Optimize backdrop filters and hardware acceleration for iOS
- Fix viewport height issues with mobile Safari fallbacks
- Update membership fee config and add IBAN payment details
- Prevent horizontal scrolling and improve mobile UX

plugins/03.mobile-safari-fixes.client.ts

@@ -0,0 +1,23 @@
+/**
+ * Mobile Safari Fixes Plugin
+ * Applies mobile Safari specific optimizations on client side
+ */
+
+import { applyMobileSafariFixes } from '~/utils/mobile-safari-utils';
+
+export default defineNuxtPlugin(() => {
+  // Apply mobile Safari fixes on client-side mount
+  if (typeof window !== 'undefined') {
+    // Apply fixes immediately
+    applyMobileSafariFixes();
+    
+    // Also apply on route changes (for SPA navigation)
+    const router = useRouter();
+    router.afterEach(() => {
+      // Small delay to ensure DOM is ready
+      nextTick(() => {
+        applyMobileSafariFixes();
+      });
+    });
+  }
+});