Fix styling: action button overflow and increase API key header height

- Change action button overflow from hidden to visible to fix visual issues
- Increase API key header window height from 220px to 300px for better fit with provider dropdown

src/app/ApiKeyHeader.js

@@ -205,7 +205,7 @@ export class ApiKeyHeader extends LitElement {
             cursor: pointer;
             transition: background 0.15s ease;
             position: relative;
-            overflow: hidden;
+            overflow: visible;
         }
 
         .action-button::after {

src/app/HeaderController.js

@@ -316,7 +316,7 @@ class HeaderTransitionManager {
         if (!window.require) return;
         return window
             .require('electron')
-            .ipcRenderer.invoke('resize-header-window', { width: 285, height: 220 })
+            .ipcRenderer.invoke('resize-header-window', { width: 285, height: 300 })
             .catch(() => {});
     }