Fix: re-organized dialog and notification z-indices

- Notifications and toasts now appear higher than dialogs when appearing together
- Standardized dialog z-index
- Added documentation for z-index guide

src/components/ImageMethodDialog.vue

@@ -1,5 +1,5 @@
 <template>
-  <div v-if="visible" class="dialog-overlay z-[60]">
+  <div v-if="visible" class="dialog-overlay">
     <div class="dialog relative">
       <div class="text-lg text-center font-bold relative">
         <h1 id="ViewHeading" class="text-center font-bold">