fix: recolour original theme to a red field with white text

Switch the original theme to a red background with white message text, with
navy buttons, evoking the red B07/B99 stock. Red/white/blue are all retained.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

styles.css

@@ -21,14 +21,14 @@
 
 /* Original DLR — 1987 red, white and blue */
 [data-theme="original"] {
-  --bg: #f5f0e1;
+  --bg: #c8102e;
   --surface: #002b5c;
-  --text: #002b5c;
-  --message: #002b5c;
-  --button-bg: #c8102e;
+  --text: #f5f0e1;
+  --message: #f5f0e1;
+  --button-bg: #002b5c;
   --button-text: #f5f0e1;
-  --button-active-bg: #002b5c;
-  --button-active-text: #f5f0e1;
+  --button-active-bg: #f5f0e1;
+  --button-active-text: #002b5c;
 }
 
 * {