feat(pagination): add pagination utility functions for handling page size and continuation tokens

- Introduced `PaginationRequest` interface to define pagination parameters.
- Implemented `parsePagination` function to extract and validate pagination parameters from a URL.
- Added `encodeContinuationToken` and `decodeContinuationToken` functions for managing continuation tokens.
- Ensured that pagination respects maximum page size limits defined in configuration.

src/utils/pagination.ts

@@ -0,0 +1,38 @@
+import { LIMITS } from '../config/limits';
+
+const MAX_PAGE_SIZE = LIMITS.pagination.maxPageSize;
+
+export interface PaginationRequest {
+  limit: number;
+  offset: number;
+}
+
+export function parsePagination(url: URL): PaginationRequest | null {
+  const pageSizeRaw = url.searchParams.get('pageSize');
+  const continuationToken = url.searchParams.get('continuationToken');
+  if (!pageSizeRaw && !continuationToken) return null;
+
+  const pageSize = pageSizeRaw ? Number(pageSizeRaw) : LIMITS.pagination.defaultPageSize;
+  if (!Number.isInteger(pageSize) || pageSize <= 0) return null;
+
+  const limit = Math.min(pageSize, MAX_PAGE_SIZE);
+  const offset = decodeContinuationToken(continuationToken);
+
+  return { limit, offset };
+}
+
+export function encodeContinuationToken(offset: number): string {
+  return btoa(String(offset));
+}
+
+export function decodeContinuationToken(token: string | null): number {
+  if (!token) return 0;
+  try {
+    const decoded = atob(token);
+    const offset = Number(decoded);
+    if (!Number.isInteger(offset) || offset < 0) return 0;
+    return offset;
+  } catch {
+    return 0;
+  }
+}