fix(dashboard): make FieldStatusCard rows keyboard-accessible [Phase 2f]

[barach6662001-bit]

Phase 2f — FieldStatusCard keyboard accessibility

Closes the last low-risk plain <div onClick> row finding from the Phase 2e clickable-elements audit (Finding 1). Identical surgical pattern to #629 (FieldCard, Phase 2b) and #633 (UpcomingPanel, Phase 2d) — no redesign.

Before

The header Усі поля CTA and the empty-state Додати поле CTA were already real <button>s — verified in Phase 2e (they are listed in the audit's false-positives appendix). The remaining debt was the per-row wrapper:

<div className={s.row} onClick={() => navigate('/fields')}>
  {/* field name, area bar, crop tag, area text */}
</div>

With cursor: pointer in the CSS module but no role, no tabIndex, no onKeyDown, no accessible name.

After

Same contract as #629 / #633:

• role="button" + tabIndex={0} + onKeyDown (Enter / Space + preventDefault on Space)
• Unrelated keys (Tab, Escape, Shift, arrows) are ignored
• aria-label mirrors the visible row content: "{fieldName}, {cropLabel}, {area} га"
• Decorative cropTag / area / bar carry aria-hidden="true" — their content is already in aria-label (the bar has no text of its own; it is a pure visual indicator)
• Token-driven :focus-visible ring in the CSS module (outline: 2px solid var(--brand); outline-offset: 2px;) paired with the existing .row:hover background, so keyboard and mouse focus look identical

Why field-specific labels for a shared destination

Every row navigates to the same /fields page, but assistive-tech users still need to tell rows apart. This deliberate decision matches the explicit recommendation in the audit.

Why no "decorative button → span" step

There is no nested <button> inside the row. The header Усі поля CTA lives outside the row tree. So the FieldCard / Phase 2b conversion step does not apply here.

Scope (per request)

In: FieldStatusCard.tsx, FieldStatusCard.module.css, new FieldStatusCard.test.tsx.
Out: WarehousesList, NotificationBell, CommandPalette, AppLayout, Sidebar, legacy components/dashboard/*, Card / Surface API. No new dependencies, no route changes, no API or business-logic changes, no redesign. Audit phase order preserved.

Tests (17, new file)

• Empty state (3): empty fields → placeholder; addField calls onAddField prop when supplied; falls back to navigate when prop omitted
• Render (3): one row per field with name/crop/area; caps at 6 rows when 7+ supplied; notSeeded fallback when currentCrop is missing
• Accessibility (4): aria-label format with crop; with notSeeded fallback; tabIndex=0; decorative chips/bar not exposed as buttons
• Activation (5): click; Enter; Space; Space preventDefault; ignored keys; header Усі поля button (real <button>) still works

Validation

• pnpm --filter frontend test → 116 / 116 (17 new + 99 existing)
• npx tsc -b --noEmit → clean
• npx eslint on changed files → clean
• npx vite build → green (✓ built in 31 s)