feat(front): unify all front user pages to DESIGN.md brand #5B5FED; fix decimal-rgba off-brand purples missed by hex normalization (MarketPage focus shadow, LoginPage radial glow)

frontend/src/pages/front/LandingPage.tsx

@@ -17,7 +17,7 @@ const appGradients: Record<string, string> = {
   a3: 'linear-gradient(135deg,#5B5FED 0%,#818CF8 100%)',
   a4: 'linear-gradient(135deg,#4F8DF9 0%,#38BDF8 100%)',
   a5: 'linear-gradient(135deg,#6366F1 0%,#7DD3FC 100%)',
-  a6: 'linear-gradient(135deg,#5B5FED 0%,#A78BFA 100%)',
+  a6: 'linear-gradient(135deg,#5B5FED 0%,#8185F5 100%)',
   a7: 'linear-gradient(135deg,#4F8DF9 0%,#818CF8 100%)',
   a8: 'linear-gradient(135deg,#6366F1 0%,#4F8DF9 100%)',
 };