feat(client): add Pagination component and integrate with Table and pages

- add Pagination component with prev/next, ellipsis page range, and optional page-size selector
- add Pagination and Table pagination stories (WithPagination, WithPaginationAndSizeSelector)
- extend Table with optional pageSize and pageSizeOptions props for built-in client-side pagination
- add Timestamp column to Table story fixtures
- enable pagination on all four pages with pageSize=10 and size selector
- add pagination i18n keys to en.json

client/src/pages/EnvironmentsPage.tsx

@@ -49,6 +49,8 @@ export function EnvironmentsPage() {
         rowKey={(e) => e.id}
         loading={loading}
         emptyMessage={t('environments.empty')}
+        pageSize={10}
+        pageSizeOptions={[10, 25, 50]}
       />
     </div>
   );

client/src/pages/KeysPage.tsx

@@ -36,6 +36,8 @@ export function KeysPage() {
         rowKey={(k) => k.name}
         loading={loading}
         emptyMessage={t('keys.empty')}
+        pageSize={10}
+        pageSizeOptions={[10, 25, 50]}
       />
     </div>
   );

client/src/pages/ScenariosPage.tsx

@@ -70,6 +70,8 @@ export function ScenariosPage() {
         rowKey={(s) => s.id}
         loading={loading}
         emptyMessage={t('scenarios.empty')}
+        pageSize={10}
+        pageSizeOptions={[10, 25, 50]}
       />
     </div>
   );

client/src/pages/SessionsPage.tsx

@@ -69,6 +69,8 @@ export function SessionsPage() {
         rowKey={(s) => s.id}
         loading={loading}
         emptyMessage={t('sessions.empty')}
+        pageSize={10}
+        pageSizeOptions={[10, 25, 50]}
       />
     </div>
   );