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/components/school/AddToCompareButton.tsx

@@ -9,10 +9,10 @@
  */
 
 import { useComparisonContext } from '@/context/ComparisonContext';
-import type { School, SimilarSchool } from '@/lib/types';
-import styles from './SimilarSchools.module.css';
+import type { School, NearbySchool } from '@/lib/types';
+import styles from './NearbySchools.module.css';
 
-export function AddToCompareButton({ school }: { school: SimilarSchool }) {
+export function AddToCompareButton({ school }: { school: NearbySchool }) {
   const { addSchool, removeSchool, selectedSchools } = useComparisonContext();
   const selected = selectedSchools.some((s) => s.urn === school.urn);