Initial commit: dashboard-elements-ui library

Angular library providing dashboard components including grid layout,
drag-and-drop widgets, resize handles, toolbar, config panel, layout
presets, and persistence services.

demo/src/styles.scss

@@ -0,0 +1,18 @@
+@use '@sda/dashboard-elements-ui/src/styles' as db;
+
+* {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+body {
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
+  background: #f5f5f7;
+  color: #111827;
+  min-height: 100vh;
+}
+
+html, body {
+  height: 100%;
+}