fix(vu): clip grid arc to match needle swing range so rest = proper zero

The grid pattern was a 360° repeating conic gradient (visible across
the full upper 180° arc), while the needle only swings -45..+45.
That made the rest position at -45 sit *inside* the visible arc
rather than at the leftmost gridline — looked wrong.

Now:
- Grid lines start at the -45 angle (matches needle origin)
- Conic-gradient mask clips visibility to the 90° active wedge
- Leftmost gridline now coincides with the needle's rest rotation
  → looks like a real VU meter at zero (silence)

media_server/static/css/styles.css

@@ -7056,10 +7056,20 @@ body.audio-spectrum-live .now-playing .spectrum span {
     content: "";
     position: absolute;
     inset: 0;
-    background: repeating-conic-gradient(from 195deg at 50% 100%,
-        transparent 0deg 4deg,
-        rgba(242, 235, 220, 0.08) 4deg 5deg,
-        transparent 5deg 9deg);
+    /* Grid lines every 9°, only inside the -45..+45 needle swing
+       so the leftmost line aligns with the rest position (proper zero). */
+    background: repeating-conic-gradient(from -45deg at 50% 100%,
+        rgba(242, 235, 220, 0.10) 0deg 0.6deg,
+        transparent 0.6deg 9deg);
+    /* Clip mask: only show the 90° active arc. */
+    -webkit-mask-image: conic-gradient(from -45deg at 50% 100%,
+        black 0deg,
+        black 90deg,
+        transparent 90deg 360deg);
+    mask-image: conic-gradient(from -45deg at 50% 100%,
+        black 0deg,
+        black 90deg,
+        transparent 90deg 360deg);
 }
 .now-playing .vu-meter::after {
     content: "VU";