fix(ui): update landing/welcome page

[v7ncentng]

Summary

• Replaced the native OS dropdown (mac/windows default <select> styling) in the CSV import "Map columns" step with a custom-built, fully themed listbox component that matches the rest of the app's design.
• Enlarged the "Import from CSV" modal so the column-mapping and row-review steps use most of the viewport height instead of shrinking to content, while leaving the initial file-picker step unchanged.
• Fixed usability bugs in the new dropdown: it can now be scrolled with the trackpad and navigated with arrow keys without closing unexpectedly, and it repositions itself to stay on-screen instead of rendering options unreachably off the bottom of the viewport.

Motivation

• The column-mapping dropdowns in the CSV importer were plain native <select> elements, so they rendered with the OS's default styling (system font, native borders/colors) instead of matching the app's design system used everywhere else in the popup.
• Once the modal was made taller, the dropdown menu (positioned via position: fixed) could open partially or fully below the visible viewport for rows near the bottom of the table, making the "Notes" option impossible to reach — a real workflow blocker when mapping the last column.
• The stopgap fix for reachability surfaced two more interaction bugs: scrolling inside the dropdown's own list would immediately close it (a capture-phase scroll listener wasn't distinguishing internal vs. external scroll), and arrow keys did nothing because keyboard navigation had never been implemented for the custom listbox.

Changes

• src/app/edit/components/address/CSVUploadOverlay.tsx
  • Replaced the native <select> in StepColumnMapper with a new MappingFieldSelect component: a button styled with the same OVERLAY_SELECT_WRAPPER/VALUE/ICON tokens used by other "Select" boxes in the app, plus a custom role="listbox" menu built from OVERLAY_AUTOCOMPLETE_* tokens.
  • Added viewport-aware positioning: the menu measures available space above/below its trigger and flips upward with a clamped maxHeight when there isn't enough room below, so it never renders outside the visible viewport.
  • Added full keyboard support (ArrowUp/ArrowDown to move an activeIndex highlight, Enter/Space to commit, Escape to close), synced with mouse hover, and auto-scrolls the highlighted option into view.
  • Fixed the outside-scroll-closes-menu listener to ignore scroll events that originate inside the dropdown's own list (previously any scroll, including internal, closed the menu instantly).
  • Increased the CSV-column value text from 14px to 16px/leading-6 to match the dropdown's text size, and switched the modal panel to a taller CSV_UPLOAD_OVERLAY_PANEL_TALL variant (90dvh) for the mapping and row-review steps only.
  • Ensured every mapping row has a bottom border, including the last ("Notes") row.
• src/app/edit/formStyles.v2.ts
  • Added CSV_UPLOAD_OVERLAY_PANEL_TALL (90dvh variant of the existing panel) and propagated flex-1 min-h-0 through the inner/content/top wrapper tokens so the taller panel's scrollable regions correctly fill the available height instead of leaving empty space.
  • Added a CSV-scoped CSV_UPLOAD_SELECT_PLACEHOLDER token (--edit-stone-600) so the "Select" placeholder text is darker than the app-wide default, without changing the shared OVERLAY_SELECT_PLACEHOLDER token used by other overlays (VehicleDetailsOverlay, AddressOverlay).

Validation

Frontend

• npm --prefix app/ui run lint
• npm --prefix app/ui run format:check
• npm --prefix app/ui run typecheck (ran as npx tsc --noEmit -p ., clean)
• npm --prefix app/ui run test
• npm --prefix app/ui run build
• npm --prefix app/mobile run lint
• npm --prefix app/mobile run typecheck

Backend

• Not applicable — frontend-only change.

Note: No live browser verification was performed — the Chrome automation extension was not connected in this environment. Manual QA in a real browser (especially scrolling/arrow-keying to the "Notes" option, and confirming the dropdown flips correctly near the bottom of the modal) is recommended before merge.

Risk

• Low risk, scoped to a single modal (CSVUploadOverlay.tsx) and its dedicated style tokens; no shared components were changed except additive tokens in formStyles.v2.ts.
• The custom dropdown reimplements keyboard/focus/ARIA behavior that native <select> provided for free — worth a manual accessibility pass (screen reader, tab order) since this isn't covered by typecheck/lint.

Rollout and Recovery

• Standard PR merge; no feature flag, migration, or data changes involved.
• Rollback is a plain revert of this PR — no persisted state or schema changes to unwind.