Fix extra empty space at bottom of pages

- Remove min-height from main-content
- Remove flex: 1 from page-content and admin-tab-swipe
- Content areas no longer expand to fill viewport height

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/styles/Layout.css

@@ -17,8 +17,6 @@
 .main-content {
   flex: 1;
   margin-left: var(--sidebar-width);
-  min-height: 100vh;
-  min-height: 100dvh;
   display: flex;
   flex-direction: column;
   transition: margin-left 0.3s ease;
@@ -396,7 +394,6 @@ label,
 
 /* Main content wrapper - with symmetric padding from sidebar edge to window edge */
 .page-content {
-  flex: 1;
   padding: var(--page-padding-y) var(--page-padding-x) 0;
   width: 100%;
   max-width: var(--page-max-width);
@@ -667,8 +664,6 @@ label,
   width: 100%;
   max-width: none;
   margin: 0;
-  flex: 1 1 auto;
-  min-height: 0;
 }
 
 /* Swipeable tab panels */