Centre-align MapPin price text under provider name

Visually reviewed in Storybook — left-aligned price looked unbalanced.
Centring both lines makes the pin read as a cohesive label rather
than a misaligned mini card.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/atoms/MapPin/MapPin.tsx

@@ -136,7 +136,7 @@ export const MapPin = React.forwardRef<HTMLDivElement, MapPinProps>(
           sx={{
             display: 'flex',
             flexDirection: 'column',
-            alignItems: 'flex-start',
+            alignItems: 'center',
             maxWidth: MAX_WIDTH,
             py: 0.5,
             px: PIN_PX,