feat: add modular sidebarLoader to all missing pages

- Replace hardcoded inline sidebar markup with <div id="sidebar-container">
  on: aboutMain, newsMain, productMain, serviceMain, contactMain
- Add sidebar-container + sidebarLoader.js script to pages that had no
  sidebar at all: newsArticle1, newsArticle2, productSeparateCommerceLNG,
  productSeparateCommercePNG, productSeparateProductionPRU,
  productSeparateProductionGasMeter, productSeparateProductionVaporizer,
  productSeparateProductionPressureRegulatorValve
- Sidebar HTML/CSS/JS is now loaded dynamically from /components/sidebar/
  on all 14 pages (mobile breakpoint ≤768px)"

views/newsPages/newsArticle2/newsArticle2.html

@@ -25,6 +25,9 @@
     <!-- Header Component -->
     <div id="header"></div>
 
+    <!-- Sidebar Component -->
+    <div id="sidebar-container"></div>
+
     <div class="container my-4 my-md-5 overflow-hidden">
       <div class="row justify-content-center">
         <div class="col-12 col-md-10 col-lg-8">
@@ -314,6 +317,7 @@
     <div id="footer"></div>
 
     <script src="components/header/headerLoader.js"></script>
+    <script src="/components/sidebar/sidebarLoader.js"></script>
     <script src="/components/footer/footerLoader.js"></script>
     <script src="newsPages/newsArticle1/newsArticle1.js?v=1.0"></script>
   </body>