Add user preference for black vs white display order

- Gear icon in header opens settings modal
- Preference stored in cookie for server-side Velocity rendering
- ViewServlet reads blackFirst cookie into Velocity context
- Velocity conditionals in pairing, results, and result-sheets templates

view-webapp/src/main/sass/main.scss

@@ -523,10 +523,22 @@
     }
   }
 
-  #logout {
+  #logout, #settings {
     cursor: pointer;
   }
 
+  #settings-modal {
+    .setting {
+      margin: 0.5em 0;
+      label {
+        display: flex;
+        align-items: center;
+        gap: 0.5em;
+        cursor: pointer;
+      }
+    }
+  }
+
   @media screen {
     #players-list {
       font-size: smaller;