significant expansion of scss styling, incl. new _dashboard.scss sheet & comprehensive primary btn theme synced w. user palette; changes to all other scss files; list.html & base.html retrofitted w. corresponding scss classes

src/static_src/scss/_palette-picker.scss

@@ -1,13 +1,21 @@
-.palette-picker {
+.palette {
     display: flex;
-    gap: 1rem;
+    flex-direction: row;
+    overflow-x: auto;
+    overflow-y: hidden;
+    scroll-snap-type: x mandatory;
+    -webkit-overflow-scrolling: touch;
+    gap: 0.75rem;
+    padding-bottom: 0.5rem;
 }
 
-.palette-picker-item {
+.palette-item {
     display: flex;
     flex-direction: column;
     align-items: center;
     gap: 0.5rem;
+    flex: 0 0 calc(100% / 3);
+    scroll-snap-align: start;
 }
 
 .swatch {