Migrate 25 custom HTML assessments into existing Next.js + Supabase platform, plus client portal v1

We run a production web platform for a professional-services firm: Next.js 16, React 19, Tailwind 4, Supabase (Postgres, Auth, Storage), deployed on Vercel. Already live: tokenized invite links, progressive autosave, per-user records, weighted scoring with AI-generated summary reports, multi question types, link revocation and expiry, rate limiting, data erasure with audit log. Fixed-price scope: Two new interactive input widgets: a 0-100 slider with an attached comment field, and a custom SVG "segment dial" click-to-rate widget. Both touch-first and theme-able. A sectioned, design-token rendering mode so imported questionnaires keep their original look (palette, fonts, section intros) instead of platform styling. Per-questionnaire scoring definitions (bands, thresholds, labels) carried in data and applied in results; the platform's generic scoring becomes fallback only. Migration of about two dozen existing single-file HTML questionnaires (they collapse into about 5 template families) into the platform. Each one verified side by side against the original, scoring verified with known-answer fixtures, mobile pass per family. An import pipeline: admin uploads an HTML file or points at a URL behind Basic auth; server-side LLM-assisted extraction to a validated JSON form spec; hard validation (whitelisted block types, every input maps to a field, size caps); preview, confirm, publish. Uploaded code must never execute client-side; everything re-renders from platform components. Participant portal v1: persistent revocable magic link per participant; portal home lists pending and completed questionnaires and explicitly shared results; a materials section the admin adds files and links to; strict per-participant isolation (row-level security); mobile. Regression on the four existing question types plus editor and generator, security pass (row-level security checks, validator bypass attempts), production deploy. Acceptance: a live demo of the full loop (invite link, autosave, complete, scored result in the participant record, portal shows the completed work and a shared material, then a questionnaire imported and published through the upload page with no code changes), with all migrations verified. In your proposal please give: fixed price, timeline, and specifically how you would verify scoring fidelity per migrated questionnaire and per-participant isolation in the portal.