Add Angular Material

Integrated @angular/material and @angular/cdk into the project and created a custom theme using SCSS. Updated angular.json to include the new theme, added Roboto and Material Icons fonts in index.html, and improved global styles for Material compatibility.

angular.json

@@ -37,6 +37,7 @@
               }
             ],
             "styles": [
+              "src/custom-theme.scss",
               "src/styles.css"
             ]
           },