Fix hero section structure - remove order classes, add missing classes

Changes:
- Removed order-2 lg:order-1 from 9 pages (image now on LEFT)
- Added bg-white/10 p-2 to image containers in 8 pages
- Added lg:py-24 padding to sections in 8 pages

Pages fixed: durgo-avvs, grilles, water-pump, pipe-coupling,
ท่อ-hdpe, ท่อ-ppr-scg, ท่อ-ppr-thai-ppr, ท่อ-syler, ท่อ-upvc,
ระบบน้ำ, วาล์ว-valve, เครื่องเชื่อม-hdpe, เครื่องเชื่อม-ppr

src/pages/ท่อ-upvc.astro

@@ -41,7 +41,7 @@ import BaseLayout from '@/layouts/BaseLayout.astro';
     </div>
     <div class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-16">
         <div class="grid lg:grid-cols-2 gap-12 items-start">
-          <div class="order-2 lg:order-1">
+          <div class="">
             <span class="inline-block px-4 py-1.5 bg-white/20 text-white rounded-full text-sm font-medium mb-4">ท่อ UPVC</span>
             <h1 class="text-3xl sm:text-4xl lg:text-5xl font-bold mb-4">ท่อ UPVC (Unplasticized Polyvinyl Chloride)</h1>
             <p class="text-lg text-primary-100 mb-8 leading-relaxed">
@@ -82,9 +82,9 @@ import BaseLayout from '@/layouts/BaseLayout.astro';
               </a>
             </div>
           </div>
-          <div class="order-1 lg:order-2">
+          <div class="">
             <div class="lg:sticky lg:top-24">
-            <div class="rounded-2xl overflow-hidden">
+            <div class="rounded-2xl overflow-hidden bg-white/10 p-2">
               <img src="/images/products-cropped/upvc-pipe_000C.jpg" alt="ท่อ UPVC" class="w-full" loading="eager" />
             </div>
           </div>