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/residential/residential-interest-detail.tsx

@@ -87,9 +87,9 @@ export function ResidentialInterestDetail({ interestId }: { interestId: string }
         </Link>
       </div>
 
-      <div className="rounded-xl border border-slate-200 bg-gradient-brand-soft px-5 py-4 shadow-xs">
+      <div className="rounded-xl border border-border bg-gradient-brand-soft px-5 py-4 shadow-xs">
         <p className="text-xs uppercase font-semibold tracking-wide text-brand">
-          Residential Interest
+          Residential interest
         </p>
         {interest.client && (
           <h1 className="mt-1 truncate text-2xl font-bold tracking-tight text-foreground">

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,