feat(i18n): Aktionsleiste + Sidebar (Quellen, Feedback, Archiv, Stats, Empty-States)

- 5 Action-Buttons im Header (Aktualisieren/Bearbeiten/Bericht
  exportieren/Archivieren/Loeschen) via data-i18n.
- Sidebar Archiv-Section, Quellen-Button, Feedback-Button, title-
  Attribute via data-i18n + data-i18n-attr.
- Sidebar-Stats 0 Quellen / 0 Artikel: app.js.updateSidebarStats
  baut die Suffixe ueber T() zusammen.
- Empty-States Kein Live-Monitoring / Keine Deep-Research (inkl.
  eigene-Filter-Varianten) lokalisiert.
- Cache-Buster app.js auf v=20260513g.

src/static/i18n/en.json

@@ -1,6 +1,22 @@
 {
   "sidebar.live_monitoring": "Live monitoring",
   "sidebar.research": "Research",
+  "sidebar.archive": "Archive",
+  "sidebar.sources": "Sources",
+  "sidebar.feedback": "Feedback",
+  "sidebar.manage_sources_title": "Manage sources",
+  "sidebar.feedback_title": "Send feedback",
+  "sidebar.stat.sources_suffix": "sources",
+  "sidebar.stat.articles_suffix": "articles",
+  "sidebar.empty_adhoc": "No live monitoring",
+  "sidebar.empty_adhoc_mine": "No own live monitoring",
+  "sidebar.empty_research": "No deep research",
+  "sidebar.empty_research_mine": "No own deep research",
+  "action.refresh": "Refresh",
+  "action.edit": "Edit",
+  "action.export": "Export report",
+  "action.archive": "Archive",
+  "action.delete": "Delete",
   "sidebar.empty": "No situations yet",
   "header.logout": "Sign out",
   "header.new_incident": "+ New situation",