feat(lyrics): active-line color picker, uppercase toggle, bigger L/XL

Add two persisted prefs to the lyrics sidebar display controls:

- activeColor: hex color override for the karaoke/active-line accent.
  Empty string means follow the theme's --accent-primary. Rendered via
  a new --lyrics-active-color CSS custom property set inline on the
  LyricsLines container; all four references to --accent-primary in
  the active-line gradient and glow shadows now fall back through it.
  Popover row shows a native color input plus a 'Theme' clear button
  that appears only when a custom color is set.

- uppercase: render all lines as uppercase in the sidebar. Applied via
  text-transform on .lyrics-lines.compact.uppercase. Switch toggle in
  the popover.

Bump L and XL sidebar sizes by the requested amount:
- L: 17/20 -> 18/21
- XL: 20/24 -> 22/26
(small and medium are unchanged.)

Both new prefs persist per-user in the same localStorage payload via
the existing sanitize/reload flow, and the hex validator rejects
malformed values on read.

cc

src/lib/i18n/locales/de.json

@@ -628,6 +628,9 @@
         "soft": "Leicht",
         "strong": "Stark"
       },
+      "activeColor": "Aktive Farbe",
+      "useThemeColor": "Design",
+      "uppercase": "Großbuchstaben",
       "reset": "Zurücksetzen"
     },
     "noLyrics": "Keine Songtexte verfügbar",