refactor(admissions): rename published_admission_number to places_offered

The staging model aliased EES's total_number_places_offered column as
published_admission_number, but PAN is the school's published capacity
(not exposed by EES at school level) — what we actually have is the
count of places offered in a given admissions round. The misnomer
propagated to the mart, SQLAlchemy model, API response, TS types, and
UI copy ("places per year", "(PAN)").

Rename end-to-end and fix the UI labels:
  - "29 places for 42 first-choice applications"
      → "29 places offered for 42 first-choice applications"
  - "Reception/Year 7 places per year"
      → "Reception/Year 7 places offered"
  - drop the misleading "(PAN)" suffix in the secondary view

Also add a comment in stg_ees_admissions clarifying this is the number
of places offered, not PAN. Requires dbt to rebuild fact_admissions
(marts are materialized as tables) before the backend can start.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nextjs-app/components/SecondarySchoolDetailView.tsx

@@ -641,10 +641,10 @@ export function SecondarySchoolDetailView({
           )}
 
           <div className={styles.metricsGrid}>
-            {admissions.published_admission_number != null && (
+            {admissions.places_offered != null && (
               <div className={styles.metricCard}>
-                <div className={styles.metricLabel}>Year 7 places per year (PAN)</div>
-                <div className={styles.metricValue}>{admissions.published_admission_number}</div>
+                <div className={styles.metricLabel}>Year 7 places offered</div>
+                <div className={styles.metricValue}>{admissions.places_offered}</div>
               </div>
             )}
             {admissions.total_applications != null && (