global refactoring

src/styles/index.css

@@ -0,0 +1,7 @@
+/* Entry point — import order matters */
+@import './base.css';     /* variables, reset, keyframes  */
+@import './layout.css';   /* app shell, topbar, feed      */
+@import './sidebar.css';  /* left nav + right panel       */
+@import './card.css';     /* ad card component            */
+@import './modal.css';    /* modal, form, image upload    */
+@import './ui.css';       /* buttons, states, spinner     */