feat(tender-radar): add settings gear link on module page

The tender-radar settings page (with the E-Mail-Alerts form) was only
reachable by manually typing the literal URL /modules/tender-radar/settings
— no on-screen link existed, and appending /settings to the dynamic
[category]/[moduleSlug] URL returns 'Modul nicht gefunden'. Add a gear-icon
Link (mirroring dkv-fleet's pattern) pointing at the literal settings route,
plus a tenderRadar.page.settingsTitle key in de/en.

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

apps/web/src/messages/de.json

@@ -575,7 +575,8 @@
   "tenderRadar": {
     "page": {
       "title": "Ausschreibungs-Radar",
-      "loading": "Lädt…"
+      "loading": "Lädt…",
+      "settingsTitle": "Einstellungen"
     },
     "results": {
       "colTitle": "Titel",