Refactor: unify dialog styles across components

- Add unified .dialog-overlay and .dialog classes to tailwind.css
- Remove duplicated dialog styles from 9 Vue components
- Standardize z-index to 50 for all dialogs
- Preserve special cases: FeedFilters (z-index: 100), PhotoDialog (camera styles)
- Eliminate ~200 lines of duplicated CSS code
- Updated ContactNameDialog from using getter methods to direct CSS classes
- Improve maintainability with single source of truth for dialog styling

src/components/GiftedPrompts.vue

@@ -291,27 +291,3 @@ export default class GivenPrompts extends Vue {
   }
 }
 </script>
-
-<style>
-.dialog-overlay {
-  z-index: 50;
-  position: fixed;
-  top: 0;
-  left: 0;
-  right: 0;
-  bottom: 0;
-  background-color: rgba(0, 0, 0, 0.5);
-  display: flex;
-  justify-content: center;
-  align-items: center;
-  padding: 1.5rem;
-}
-
-.dialog {
-  background-color: white;
-  padding: 1rem;
-  border-radius: 0.5rem;
-  width: 100%;
-  max-width: 500px;
-}
-</style>