Merge remote changes, standardize button text color to --text-white CSS variable

Resolved merge conflicts by keeping the CSS variable approach (var(--text-white))
instead of hardcoded #fff for button text colors across all components.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/melodies/MelodyDetail.jsx

@@ -143,7 +143,7 @@ export default function MelodyDetail() {
             <button
               onClick={() => setShowDelete(true)}
               className="px-4 py-2 text-sm rounded-md transition-colors"
-              style={{ backgroundColor: "var(--danger)", color: "var(--text-white)" }}
+              style={{ backgroundColor: "var(--danger-btn)", color: "var(--text-white)" }}
             >
               Delete
             </button>