Fix dark theme background issue

- Replace hardcoded white background with dynamic theme colors
- Main content container now properly switches between light/dark themes
- Improved box shadow for better visibility in both themes

shared_styling.py

@@ -103,9 +103,9 @@ def get_base_css():
     .main .block-container {{
         padding-top: 2rem;
         padding-bottom: 2rem;
-        background-color: rgba(255, 255, 255, 0.9);
+        background-color: {get_current_colors()['background']};
         border-radius: 15px;
-        box-shadow: 0 4px 20px rgba(0, 0, 0, 0.03);
+        box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
         margin-top: 1rem;
         color: {get_current_colors()['text_primary']} !important;
     }}