Fix Settings black-on-black contrast (Gitea #75)

Scope .settings styles to the panel: light #eee text on the dark
#121212 surface for labels, and white inputs/selects/options with dark
text. Both pairs exceed WCAG 4.5:1. Add settings-contrast e2e as the
regression guard for the Settings form plus the sibling dev panels.

frontend/src/create/settings/Settings.svelte

@@ -181,8 +181,18 @@
 </div>
 
 <style>
-  .settings { max-width: 600px; }
-  label { display: block; margin: 8px 0 4px; }
-  input, select { width: 100%; padding: 6px; }
-  button { margin-top: 16px; }
+  .settings { max-width: 600px; color: #eee; }
+  .settings label { display: block; margin: 8px 0 4px; }
+  .settings input,
+  .settings select {
+    color: #eee;
+    background: #1c1c1c;
+    width: 100%;
+    padding: 6px;
+  }
+  .settings option {
+    color: #eee;
+    background: #1c1c1c;
+  }
+  .settings button { margin-top: 16px; }
 </style>