Wire search to map pin; handle centroid form API

Connect search results to the map by introducing a pin state in app/page and passing it to Map and Search. Add marker component and icon (components/marker.tsx), display a Marker on the map, and prepare a PanToPoint helper (commented). Update the search component to use typed Prisma models, accept an onPinChange callback, build logic to determine the location 'kods', POST it as FormData to /api/center, and place the returned dd_n/dd_e as a map pin. Adjust the API route to read formData and query prisma.centroidi by kods. Update Prisma schema: remove obsolete apstipr/apst_pak fields and change dd_e/dd_n to Decimal(9,7). Also minor cleanups: remove extra blank lines in not-found, add small comments and todos.
