fix(visual): KPITile data-testid + restore residential interest casing

Post-PR10c follow-ups discovered during smoke triage:
- KPITile gets data-testid="kpi-tile" so the dashboard smoke spec's
  '[data-testid*="kpi"]' selector matches (test 10-dashboard:27 expected
  >=4 kpi cards; the old Card-based render was matched by the
  '[class*="card"]' branch and didn't need a testid).
- Residential interest detail eyebrow text reverted from "Residential
  Interest" to "Residential interest" (lowercase i). The visual is
  identical because the wrapper has the `uppercase` class; the smoke
  spec at 26-residential:140 looks for the literal lowercase string.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/ui/kpi-tile.tsx

@@ -43,6 +43,7 @@ export function KPITile({
 
   return (
     <div
+      data-testid="kpi-tile"
       className={cn(
         'group relative overflow-hidden rounded-xl border border-border bg-gradient-brand-soft p-5 shadow-sm transition-all duration-base ease-smooth hover:shadow-md',
         className,