Refactor contact management functions and remove phpinfo.php

- Updated formatting and structure of functions in edit_contact.inc.php for better readability and consistency.
- Added comments to clarify the purpose of certain code sections, especially regarding mandant handling.
- Removed the deprecated phpinfo.php file to clean up the codebase.

layout/admin/css/mysyde.css

@@ -5570,6 +5570,23 @@ li#user_menu ul {
     height: auto;
 }
 
+.main_menu.main_navigation {
+    overflow-y: auto !important;
+    height: calc(100dvh - 160px - 70px) !important;
+    display: block !important;
+    width: calc(100% - 1px) !important;
+    padding-bottom: 40px !important;
+}
+
+.main_menu:nth-child(2) {
+    position: fixed !important;
+    bottom: 0 !important;
+    left: 0 !important;
+    width: 286px !important;
+    z-index: 10 !important;
+    border-top: 1px solid var(--rahmen-toggle) !important;
+}
+
 /*
 * === Specific styles for structure nav (without gray background) =============
 */