style(frontend): responsive polish pass for narrow viewports

Part of the Ombrora Convert redesign (Task 5/5).

frontend/src/styles/home.css

@@ -92,3 +92,17 @@
     flex: 1 1 auto;
   }
 }
+
+@media (max-width: 480px) {
+  .hero {
+    padding: 2rem 1rem;
+  }
+
+  .hero h1 {
+    font-size: 1.75rem;
+  }
+
+  .dropzone {
+    padding: 1.75rem 1rem;
+  }
+}

frontend/src/styles/layout.css

@@ -48,3 +48,17 @@
   border-top: 1px solid var(--color-border);
   font-size: 0.875rem;
 }
+
+@media (max-width: 480px) {
+  .site-header {
+    padding: 0.75rem 1rem;
+  }
+
+  .brand {
+    font-size: 1.05rem;
+  }
+
+  .site-header-controls {
+    gap: 0.5rem;
+  }
+}