fix: improve Coloris color picker visibility and button clickability

- Fix grid layout: add second column for input (grid-template-columns: var(--input-h) 1fr)
- Ensure color picker button is clickable with cursor pointer and pointer-events auto
- Set color picker z-index to 10000 to display above all UI elements
- Add global styles to ensure Coloris button is always clickable

Fixes issues where:
- Color picker appeared behind ElementPopup
- Button was not consistently clickable
- Grid layout was missing second column definition

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

src/App.vue

@@ -675,6 +675,19 @@ onMounted(async () => {
   height: 1.5rem;
 }
 
+/* Coloris color picker - ensure it's always on top */
+:deep(.clr-picker) {
+  z-index: 10000 !important;
+}
+
+/* Coloris button - ensure it's clickable and visible */
+:deep(.clr-field button) {
+  pointer-events: auto !important;
+  cursor: pointer !important;
+  position: relative;
+  z-index: 1;
+}
+
 /* Hide UI elements when printing */
 @media print {
   #editor-panel,