🎨 Improve styling for the header background

🌟 Enhance the visual appeal of the header background with custom colors and filters.
🎨 Refactor code by importing theme colors and custom styles.
📅 Add date picker styles to improve UI consistency.
🔧 Update header import to ensure proper functionality.

src/styles/_header.scss

@@ -0,0 +1,3 @@
+.nc-header-bg {
+  @apply bg-white/70 dark:bg-neutral-900/60 backdrop-blur-2xl backdrop-filter;
+}

src/styles/index.scss

@@ -0,0 +1,5 @@
+@import "./_theme_colors";
+@import "./_theme_custom";
+@import "./_dates_picker";
+//
+@import "./header";