Senior Frontend Product Engineer / SaaS UI Uplift

Scope of Work We need a senior frontend developer to improve the look, usability, and reliability of an existing web application. The application already exists. The work is to take existing screens and approved design references, then upgrade the live application screen by screen so it looks modern, polished, professional, and works properly. Specific Outcomes Required 1. Review the current screen before changing anything For each page, you must first review: * the current live screen * the approved design/mock-up * the existing frontend code * the API/backend data currently used by the screen * the buttons, cards, forms, tables, tabs, modals, and actions on the page You must then provide a short checklist showing: * what already matches the design * What does not match * What is missing * What is broken * What backend data is required * What can be fixed immediately * what cannot be fixed without backend support 2. Rebuild the frontend to match the approved design You will update the frontend so each page: * looks modern and premium * matches the approved design as closely as possible * has cleaner spacing, layout, typography, and visual hierarchy * has polished cards, buttons, tabs, forms, and tables * works on desktop and mobile * has proper loading, empty, error, and success states 3. Wire the page to real backend data Every visible value must come from a real source. Do not use fake data. Do not hardcode business numbers. Do not create fake customer names, invoices, charts, usage numbers, payment states, or connection states. If the backend does not provide the data needed for the design, you must clearly identify the missing API or field and show an honest empty/unavailable state in the UI. 4. Test every component on the page For each completed page, you must test: * every button * every link * every tab * every modal * every drawer * every form * every card * every table * every loading state * every empty state * every error state * mobile layout * browser console errors * network/API errors Nothing should be marked complete unless it has been tested. 5. Provide proof of completion For every completed page, provide: * screenshot before changes * screenshot after changes * screenshot on desktop * screenshot on mobile * list of files changed * list of backend/API endpoints used * list of buttons/actions tested * any remaining issues or blockers 6. Work one page at a time Do not attempt to redesign the whole platform at once. The process should be: 1. Review one page. 2. Provide a gap checklist. 3. Fix that page. 4. Test that page. 5. Provide screenshots and proof. 6. Move to the next page. First Page to Review The first task will be one page only. You will be asked to review the current page against the approved design and provide: * gap checklist * component list * backend/API data requirements * testing checklist * implementation estimate After that is approved, you will complete the implementation. Pages Likely to Be Included The application includes pages such as: * Billing and subscription * Settings * Integrations / connected apps * Reports * Dashboard-style pages * AI assistant page * Documents / files * Calendar / inbox-style pages * Admin pages You do not need to understand the full business on day one. You need to be able to review a screen, understand what it should look like, wire it to real data, and test it properly. What We Are Looking For We need someone who can deliver working product screens, not just attractive mock-ups. The right person will be able to: * improve visual quality * write clean React code * connect frontend components to APIs * test their own work * explain what is missing clearly * avoid fake data * provide proof that the work is live and working What We Do Not Want Do not apply if you only do: * landing pages * static HTML * basic website design * Figma-only design * template-based dashboards * visual-only work without testing * frontend screens with fake data This job requires frontend engineering, product judgment, and testing discipline.