fix(mobile): move modals to document.body to escape panel DOM constraints

Fix mobile modal positioning by moving modals to document.body on first use.

Root cause: Modals were nested inside .rpg-panel which has 'transform' in
its transition property (line 40 of style.css). This creates a containing
block that constrains position:fixed children to the panel viewport instead
of the document viewport, causing modals to be cut off on mobile.

Changes:

1. confirmDialog.js - Modified showConfirmDialog() and showAlertDialog():
   - Check if modal is already in document.body container
   - Create 'document-body-modals' container at body level (once)
   - Move modal to body container to escape panel constraints
   - Container has pointer-events: none to pass clicks through
   - Individual modals have pointer-events: auto to receive clicks

2. style.css - Added pointer-events: auto to .rpg-modal:
   - Ensures clicks work when modal is in pointer-events: none container

Result:
- Modals now render over entire SillyTavern viewport
- Properly centered with full z-index stacking
- No longer constrained by panel's transform/stacking context
- Works correctly on both desktop and mobile

style.css

@@ -1441,6 +1441,7 @@ body:has(.rpg-panel.rpg-position-left) #sheld {
     justify-content: center;
     align-items: center;
     padding: 1rem; /* Ensure content doesn't touch screen edges on mobile */
+    pointer-events: auto; /* Ensure clicks work when moved to body container */
 }
 
 /* Modal Content Container */