Add audio sources as first-class entities, add mapped CSS type, simplify target editor for mapped sources

- Audio sources moved to separate tab with dedicated CRUD API, store, and editor modal
- New "mapped" color strip source type: assigns different CSS sources to distinct LED sub-ranges (zones)
- Mapped stream runtime with per-zone sub-streams, auto-sizing, hot-update support
- Target editor auto-collapses segments UI when mapped CSS is selected
- Delete protection for CSS sources referenced by mapped zones
- Compact header/footer layout

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

server/src/wled_controller/static/css/layout.css

@@ -2,8 +2,8 @@ header {
     display: flex;
     justify-content: space-between;
     align-items: center;
-    padding: 20px 0 10px;
-    margin-bottom: 10px;
+    padding: 8px 0 6px;
+    margin-bottom: 6px;
     position: relative;
     z-index: 100;
 }
@@ -11,11 +11,11 @@ header {
 .header-title {
     display: flex;
     align-items: center;
-    gap: 10px;
+    gap: 8px;
 }
 
 h1 {
-    font-size: 2rem;
+    font-size: 1.25rem;
     color: var(--primary-text-color);
 }
 
@@ -28,7 +28,7 @@ h2 {
 .server-info {
     display: flex;
     align-items: center;
-    gap: 15px;
+    gap: 8px;
 }
 
 .header-link {
@@ -57,7 +57,7 @@ h2 {
 }
 
 .status-badge {
-    font-size: 1.5rem;
+    font-size: 1rem;
     animation: pulse 2s infinite;
 }
 
@@ -156,12 +156,12 @@ h2 {
 .theme-toggle {
     background: var(--card-bg);
     border: 1px solid var(--border-color);
-    padding: 6px 12px;
+    padding: 4px 8px;
     border-radius: 4px;
     cursor: pointer;
-    font-size: 1.2rem;
+    font-size: 1rem;
     transition: transform 0.2s;
-    margin-left: 10px;
+    margin-left: 0;
 }
 
 .theme-toggle:hover {
@@ -170,14 +170,14 @@ h2 {
 
 /* Footer */
 .app-footer {
-    margin-top: 20px;
-    padding: 15px 0;
+    margin-top: 12px;
+    padding: 6px 0;
     text-align: center;
 }
 
 .footer-content {
     color: var(--text-secondary);
-    font-size: 0.9rem;
+    font-size: 0.75rem;
 }
 
 .footer-content p {
@@ -203,7 +203,7 @@ h2 {
 @media (max-width: 768px) {
     header {
         flex-direction: column;
-        gap: 15px;
+        gap: 8px;
         text-align: center;
     }
 }