fix(content): drop @ prefix from JPPSELECTION in text + add CTA to 20 products

Two changes driven by content review:

1) @JPPSELECTION → JPPSELECTION in user-visible text only
   - 19 page files: drop @ from inline JPPSELECTION in <p> tags
   - BaseLayout.astro + Footer.astro: drop @ from companyInfo.line
     (rendered as "LINE: @JPPSELECTION" in mobile CTA + footer)
   - URL line.me/ti/p/~JPPSELECTION left unchanged (the @ belongs
     in the URL per line.me convention)

2) Add missing CTA section to all 20 product pages
   - 16 pages had no CTA at all
   - 4 pages (armflex, aeroflex, maxflex, xy-lent) had bespoke
     CTA variants; replaced with canonical template
   - Template copied from ppr-thai-ppr
   - CTA inserted before </main> in all 20 product pages

Verified rendered HTML:
- @JPPSELECTION in <p> text = 0 across all 20 pages
- "LINE: JPPSELECTION" rendered in footer / mobile CTA
- heading + contact + line buttons present in all 20

Files touched: 30

src/pages/pipe-coupling.astro

@@ -207,5 +207,15 @@ import BaseLayout from '@/layouts/BaseLayout.astro';
         </div>
       </div>
     </section>
-  </main>
+      <!-- CTA -->
+    <section class="py-16 bg-gradient-to-br from-primary-700 to-primary-600 text-white  relative overflow-hidden">
+      <div class="max-w-4xl mx-auto px-4 sm:px-6 lg:px-8 text-center">
+        <h2 class="text-3xl font-bold mb-6">สนใจสินค้านี้?</h2>
+        <p class="text-lg text-primary-100 mb-8">ติดต่อเราวันนี้ 090-555-1415 หรือแอดไลน์ JPPSELECTION</p>
+        <div class="flex flex-wrap justify-center gap-4">
+          <a href="/contact-us" class="bg-white text-primary-700 py-3 px-8 rounded-xl font-semibold hover:bg-primary-50 transition-colors">ติดต่อเรา</a>
+          <a href="https://line.me/ti/p/~JPPSELECTION" target="_blank" rel="noopener" class="bg-accent-500 hover:bg-accent-600 text-white py-3 px-8 rounded-xl font-semibold transition-colors">แอดไลน์</a>
+        </div>
+      </div>
+    </section>  </main>
 </BaseLayout>