ux: centralize state-card utility

frontend/src/components/ui/DesignSystemStyles.astro

@@ -477,6 +477,11 @@
     -webkit-backdrop-filter: blur(12px);
   }
 
+  .state-card {
+    padding: var(--ui-state-card-pad, 2.25rem 1.5rem);
+    text-align: center;
+  }
+
   .ui-btn {
     display: inline-flex;
     align-items: center;

frontend/src/pages/communities.astro

@@ -226,8 +226,12 @@ import { API_BASE as apiBase } from '../lib/api';
 </Layout>
 
 <style>
+  .ui-page {
+    --ui-state-card-pad: 2.5rem 1.5rem;
+  }
+
   .communities-toolbar {
-    padding: 1rem;
+    padding: 1rem 1.25rem;
     margin-bottom: 1.25rem;
   }
 
@@ -342,11 +346,6 @@ import { API_BASE as apiBase } from '../lib/api';
     color: rgba(255, 255, 255, 0.78);
   }
 
-  .state-card {
-    padding: 2.5rem 1.5rem;
-    text-align: center;
-  }
-
   .loading {
     color: var(--color-text-muted);
     margin: 0;

frontend/src/pages/communities/[slug]/plugins.astro

@@ -396,11 +396,6 @@ const { slug } = Astro.params;
     color: var(--color-text-muted);
   }
 
-  .state-card {
-    padding: 2.25rem 1.5rem;
-    text-align: center;
-  }
-
   .community-badge {
     padding: 1rem 1.1rem;
     margin-bottom: 1.5rem;

frontend/src/pages/proposals.astro

@@ -192,11 +192,6 @@ import { API_BASE as apiBase } from '../lib/api';
     }
   }
 
-  .state-card {
-    padding: 2.25rem 1.5rem;
-    text-align: center;
-  }
-
   .list {
     display: grid;
     gap: 1rem;