Frontend profile UI

[Zainu04]

Summary
Implements the Profile page frontend, consuming the Users endpoint from #1. Loads the current user via GET /api/users/me and lets them update display_name and home_currency via PATCH /api/users/me, with loading/success/error states and client-side validation.

New files

• client/src/pages/Profile.jsx — page component: loads current user on mount, renders view mode and an inline edit form
• client/src/pages/Profile.css — page styles (sand/beige palette)
• client/src/components/Sidebar.jsx — shared left nav shell matching the wireframes, reusable by future pages
• client/src/components/Sidebar.css — sidebar styles
• client/src/services/users.js — thin fetch wrapper around GET/PATCH /api/users/me
• client/src/helpers/currencies.js — curated {code, label} list for the home-currency select

Changes to existing files

• client/src/App.jsx — registered the /profile route
• client/src/index.css — added shared sand/beige color palette as CSS variables (--sand-*), used by Profile.css and Sidebar.css so future pages can match

Acceptance criteria

• Current user's display name and home currency appear on the Profile page
• User can update display name
• User can update home currency
• Home currency defaults to USD when no other value is set
• Submission is blocked when display name is empty/whitespace
• Save button disabled and shows "Saving…" while the PATCH request is in flight
• On update failure, existing profile info stays visible and an error message is shown
• Updated profile info appears immediately after save, no manual refresh required

Dev Notes

• No auth yet, so this consumes /me as-is per T1 — nothing here assumes a real logged-in user.
• Save intentionally updates local state from the PATCH response (not by re-fetching), so a failed save can never clobber the last-known-good profile shown on screen.
• The wireframe's stats row (Trips Completed / Upcoming Trips / Countries Visited) and the Notifications/Help & Support settings rows aren't backed by any endpoint yet — left as static "Coming soon" rows rather than faking functionality. Those depend on the Trips/Users tickets adding more fields.
• Sidebar.jsx links to routes for other pages (/dashboard, /trips, /itinerary, /budget, /packing-list) that don't exist yet — intentional, so nav is consistent once those pages land.

Testing

• Loaded /profile — confirmed seeded user (Jane Doe, USD) renders correctly

- Updated display name + home currency — confirmed `PATCH /api/users/me` returns 200, page updates without refresh, and values persist on reload

• Submitted empty display name — confirmed inline validation blocks the request (no network call fires)
• Simulated a failed update (stopped server mid-request) — confirmed error banner shows and previous profile data stays visible