Simplify school types and persist selected schools

- Add runtime normalization of cryptic school type codes to user-friendly names
  (e.g., AC/ACC/ACCS -> "Academy", CY/CYS -> "Community")
- Update SCHOOL_TYPE_MAP in schemas.py with consolidated mappings
- Add normalize_school_type() and get_school_type_codes_for_filter() helpers
- Persist selected schools in localStorage across page refreshes
- Move "Add to Compare" button from modal footer to header

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/app.js

@@ -345,6 +345,9 @@ function handleRoute() {
 document.addEventListener("DOMContentLoaded", init);
 
 async function init() {
+  // Load selected schools from localStorage first
+  loadSelectedSchoolsFromStorage();
+
   try {
     // Load filters and metrics in parallel (single request for filters)
     const [filtersData, metricsData] = await Promise.all([
@@ -376,6 +379,9 @@ async function init() {
   // Initialize tooltip manager
   tooltipManager = new TooltipManager();
 
+  // Render any previously selected schools
+  renderSelectedSchools();
+
   // Handle initial route
   handleRoute();
 
@@ -1544,14 +1550,38 @@ function addToComparison(school) {
   }
 
   state.selectedSchools.push(school);
+  saveSelectedSchoolsToStorage();
   renderSelectedSchools();
 }
 
 function removeFromComparison(urn) {
   state.selectedSchools = state.selectedSchools.filter((s) => s.urn !== urn);
+  saveSelectedSchoolsToStorage();
   renderSelectedSchools();
 }
 
+function saveSelectedSchoolsToStorage() {
+  try {
+    localStorage.setItem("selectedSchools", JSON.stringify(state.selectedSchools));
+  } catch (e) {
+    console.warn("Failed to save to localStorage:", e);
+  }
+}
+
+function loadSelectedSchoolsFromStorage() {
+  try {
+    const stored = localStorage.getItem("selectedSchools");
+    if (stored) {
+      const schools = JSON.parse(stored);
+      if (Array.isArray(schools)) {
+        state.selectedSchools = schools;
+      }
+    }
+  } catch (e) {
+    console.warn("Failed to load from localStorage:", e);
+  }
+}
+
 function showEmptyState(container, message) {
   container.innerHTML = `
         <div class="empty-state">