refactor(admin-web): drop eyebrow labels from page heroes

Remove the redundant eyebrow text above page titles in PageHero,
BrandsView and TrackingView, and clean up the now-unused i18n keys.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/admin-web/src/i18n/messages/en-US.ts

@@ -74,7 +74,6 @@ const enUS = {
     imitation: "Imitation Create",
     media: "Media",
     brandManagement: "Brand Management",
-    brands: "Brand Library",
     tracking: "Tracking",
     trackingDetail: "Data Details",
     contentManagement: "Content Management",
@@ -399,7 +398,6 @@ const enUS = {
     noRecentArticles: "No recent generations yet",
   },
   tracking: {
-    eyebrow: "AI Brand Monitoring",
     brandPlaceholder: "Select brand",
     keywordPlaceholder: "Select keyword",
     collectNow: "Collect Now",