docs: update navigation, styles and client-side guide titles

- Fixed sidebar title wrapping with custom CSS (site-title, side-bar, main-content)
- Shortened long page title for client-side build setup in nav
- Cleaned up index.md structure for adoption guides
- Added custom.css integration via _config.yml

Author: bsayli

docs/adoption/client-side-adoption-pom.md

@@ -1,6 +1,6 @@
 ---
 layout: default
-title: Client-Side Build Setup (Maven Plugins & Dependencies)
+title: Client-Side Build Setup
 parent: Client-Side Adoption
 nav_order: 1
 ---

docs/assets/css/custom.css

@@ -4,4 +4,13 @@
     white-space: normal !important;
     line-height: 1.3 !important;
     text-align: center !important;
+    padding: 0.5rem !important;
+}
+
+.side-bar {
+    width: 300px !important;
+}
+
+.main-content {
+    margin-left: 320px !important;
 }