Make table page size a configurable setting, not a hardcoded 20

Pagination just landed hardcoded to 20 rows everywhere; add a way to
change that instead of leaving it fixed for every table in the app.

pageSize joins dateFormat/timeFormat on the existing display settings
object (server-side default 20, 5-500 range enforced by the PUT
schema) rather than becoming its own settings section, since it's the
same kind of thing -- an admin-configured, globally-applied display
preference read by every signed-in role via the already-public GET
/api/settings/display endpoint, same as the date/time format already
works.

Renamed the "Date & Time" settings tab/page/route to "Display" (still
just one component, now covering both date/time format and table
pagination) since its scope no longer matches the old name -- kept
Settings.tsx's usual pattern of one page per concern rather than
adding a second, oddly-scoped tab just for one number field.

New web/src/utils/pageSize.ts mirrors utils/date.ts's existing
module-level "set once at startup, read anywhere without prop-
drilling" pattern; usePagination()'s pageSize parameter now defaults
to getPageSize() instead of a literal 20, evaluated fresh on every
call so it picks up a saved change without touching any of the ten
pages already using the hook.

Verified server-side against a temp SQLite DB: pageSize defaults to
20, a partial update sets it without disturbing dateFormat/timeFormat
and vice versa, and it persists across a fresh settings read. Also
checked the default-parameter mechanics directly (re-evaluates the
global value on every call rather than capturing it once, and an
explicit override still wins).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/App.tsx

@@ -21,10 +21,11 @@ import Synology from "./pages/Synology";
 import Settings from "./pages/Settings";
 import NotificationSettings from "./pages/settings/NotificationSettings";
 import BadgeSettings from "./pages/settings/BadgeSettings";
-import DateTimeSettings from "./pages/settings/DateTimeSettings";
+import DisplaySettings from "./pages/settings/DisplaySettings";
 import CacheSettings from "./pages/settings/CacheSettings";
 import AppShell from "./layout/AppShell";
 import { setDateTimeSettings } from "./utils/date";
+import { setPageSize } from "./utils/pageSize";
 
 const roleRank: Record<UserRole, number> = { viewer: 0, operator: 1, admin: 2 };
 
@@ -58,7 +59,10 @@ export default function App() {
         setUser(null);
       },
     );
-    api.settings.display().then((res) => setDateTimeSettings(res.display)).catch(() => {});
+    api.settings.display().then((res) => {
+      setDateTimeSettings(res.display);
+      setPageSize(res.display.pageSize);
+    }).catch(() => {});
   }, []);
 
   if (user === undefined) {
@@ -120,7 +124,7 @@ export default function App() {
           <Route index element={<Navigate to="notifications" replace />} />
           <Route path="notifications" element={<NotificationSettings />} />
           <Route path="badges" element={<BadgeSettings />} />
-          <Route path="date-time" element={<DateTimeSettings />} />
+          <Route path="display" element={<DisplaySettings />} />
           <Route path="cache" element={<CacheSettings />} />
         </Route>
       </Routes>