refactor: reorganize shared/lib into per-function subfolders

src/shared/lib/utils/formatDate/formatDate.ts

@@ -0,0 +1,31 @@
+/**
+ * Formats a PocketBase date string into a localized year string or "Present".
+ * @throws {Error} if any date is invalid or if the range is logically impossible.
+ */
+export function formatYearRange(start: string, end: string | null): string {
+  const startDate = new Date(start);
+  if (Number.isNaN(startDate.getTime())) {
+    throw new Error('Invalid start date');
+  }
+  const startYear = startDate.getFullYear();
+
+  if (end === null) {
+    return `${startYear} — Present`;
+  }
+
+  const endDate = new Date(end);
+  if (Number.isNaN(endDate.getTime())) {
+    throw new Error('Invalid end date');
+  }
+  const endYear = endDate.getFullYear();
+
+  if (startYear > endYear) {
+    throw new Error('Start year cannot be after end year');
+  }
+
+  if (startYear === endYear) {
+    return `${startYear}`;
+  }
+
+  return `${startYear} — ${endYear}`;
+}