style(dashboard): fix bunched buttons in card headers

This commit adds a proper flexbox layout to the '.card-actions' CSS class. Previously, action buttons (like Export and Refresh on the Analytics page) were bunching up because they lacked a flex container with appropriate gap and wrapping rules. It also updates the '.card-header' to wrap gracefully on smaller screens.

static/index.html

@@ -4,7 +4,7 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>LLM Proxy Gateway - Admin Dashboard</title>
-    <link rel="stylesheet" href="/css/dashboard.css?v=8">
+    <link rel="stylesheet" href="/css/dashboard.css?v=9">
     <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.4.0/css/all.min.css">
     <link rel="icon" href="img/logo-icon.png" type="image/png" sizes="any">
     <link rel="apple-touch-icon" href="img/logo-icon.png">