Music Lyrics: 가사 저장/수정/삭제 기능 추가

- AI 생성 가사 즉시 DB 저장 (세션 휘발 → 영구 보관)
- 저장된 가사 목록 자동 로드 (탭 진입 시)
- 인라인 수정: 제목 + 가사 텍스트 편집 후 저장/취소
- 개별 삭제 버튼
- api.js: getSavedLyrics, saveLyrics, updateLyrics, deleteLyrics

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

src/pages/music/MusicStudio.css

@@ -2311,6 +2311,10 @@
 .ms-lyrics-card__header {
     padding: 14px 16px 10px;
     border-bottom: 1px solid var(--ms-line-2);
+    display: flex;
+    flex-wrap: wrap;
+    align-items: baseline;
+    gap: 8px;
 }
 
 .ms-lyrics-card__title {
@@ -2340,11 +2344,75 @@
     overflow-y: auto;
 }
 
+.ms-lyrics-card__date {
+    font-family: var(--ms-ff-mono);
+    font-size: 9px;
+    color: var(--ms-dim);
+    letter-spacing: 0.04em;
+    margin-left: auto;
+    flex-shrink: 0;
+}
+
 .ms-lyrics-card__actions {
     display: flex;
     gap: 6px;
     padding: 8px 16px 12px;
     border-top: 1px solid var(--ms-line-2);
+    flex-wrap: wrap;
+}
+
+/* ── 수정 모드 ── */
+.ms-lyrics-card.is-editing {
+    border-color: var(--ms-accent);
+    box-shadow: 0 0 16px rgba(245, 166, 35, 0.08);
+}
+
+.ms-lyrics-card__title-input {
+    width: 100%;
+    background: var(--ms-surface2);
+    border: 1px solid var(--ms-line);
+    border-radius: 6px;
+    padding: 6px 10px;
+    font-family: var(--ms-ff-disp);
+    font-size: 16px;
+    letter-spacing: 0.04em;
+    color: var(--ms-text);
+    outline: none;
+    margin-bottom: 4px;
+}
+
+.ms-lyrics-card__title-input:focus {
+    border-color: var(--ms-accent);
+}
+
+.ms-lyrics-card__text-input {
+    width: 100%;
+    background: var(--ms-surface2);
+    border: none;
+    border-top: 1px solid var(--ms-line-2);
+    border-bottom: 1px solid var(--ms-line-2);
+    padding: 14px 16px;
+    font-family: var(--ms-ff-mono);
+    font-size: 12px;
+    line-height: 1.8;
+    color: rgba(255,255,255,0.85);
+    resize: vertical;
+    min-height: 200px;
+    outline: none;
+}
+
+.ms-btn--danger-text {
+    color: #e85c3a !important;
+    opacity: 0.7;
+}
+
+.ms-btn--danger-text:hover {
+    opacity: 1;
+}
+
+.ms-btn--accent.ms-btn--sm {
+    padding: 3px 10px;
+    font-size: 11px;
 }
 
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