fix(theme): readable text on the Polarized teal accent

White on #14b8a6 reaches only 2.5:1; dark teal #042f2e gives 5.8:1 for
primary buttons, counters and active filters.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/themes/theme-polarized.css

@@ -9,7 +9,7 @@
   --accent-hover: #2dd4bf;
   --accent-dim: rgba(20, 184, 166, 0.16);
   --accent-border: rgba(45, 212, 191, 0.45);
-  --text-on-accent: #ffffff;
+  --text-on-accent: #042f2e; /* dunkel: Weiß auf Türkis erreicht nur 2,5:1 */
 
   /* --- 2. OBERFLÄCHEN & HINTERGRÜNDE --- */
   --bg-app: #090e11;