feat(260723-lvg): add "Jetzt abrufen" manual poll button to tender radar

PollNowButton sits next to the settings gear in the tender-radar header,
mirrors the DKV spinner/disabled UX, and bumps a refreshKey on success to
refetch ResultsList without touching any filter. Failure surfaces an
i18n error (de/en parity). pollNow() client hits POST
/modules/tender-radar/poll-now.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/web/src/messages/en.json

@@ -576,7 +576,12 @@
     "page": {
       "title": "Tender Radar",
       "loading": "Loading…",
-      "settingsTitle": "Settings"
+      "settingsTitle": "Settings",
+      "pollNow": "Fetch now",
+      "pollNowTitle": "Fetch due sources now",
+      "polling": "Fetching…",
+      "pollError": "The fetch could not be triggered. You may not have the required permissions.",
+      "pollErrorDismiss": "Dismiss"
     },
     "results": {
       "colTitle": "Title",