SplashHandler: pass structured props (logo, app_name, voucher_code,
author, copyright) instead of HTML blob for default splash.

Splash.vue: full-screen logo-centric launch screen with entrance
animations for default splash. Card+v-html layout preserved for
custom rider->splash content.

GenericForm.vue: voucher code badge uses || CODE || framing per
Pay Code Framing Convention v1.0.

Co-Authored-By: Oz <oz-agent@warp.dev>