refactor: rename similar → nearby, so the code says what the section does

The section ranks on distance and is headed "Other schools nearby", but every
identifier still called it "similar" — the exact drift that leaves a later
reader trusting a name over the behaviour.

Mechanical: files, the module, the payload key, the type, the components, the
prop. No behaviour change; the suites are unchanged in count and still green.
Free to do now because #150 has not merged, so the payload key rename needs no
lockstep deploy. Uses of "similar" that are ordinary English — progress
measures compared to similar pupils, and unrelated comments — are untouched.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

nextjs-app/lib/types.ts

@@ -354,7 +354,7 @@ export interface SchoolsResponse {
  * version ordered by it and buried the school down the road under faith
  * matches three times further away.
  */
-export interface SimilarSchool {
+export interface NearbySchool {
   urn: number;
   school_name: string;
   distance_miles: number;
@@ -384,7 +384,7 @@ export interface SchoolDetailsResponse {
    * API that serves this must render without it. Absent and empty mean the
    * same thing here — no section.
    */
-  similar_schools?: SimilarSchool[];
+  nearby_schools?: NearbySchool[];
   yearly_data: SchoolResult[];
   absence_data: AbsenceData | null;
   // Supplementary data (null until Kestra populates)