Add split export: Export Route vs Export Plan

Split button with default "Export GPX" (track only) and dropdown:
- Export Route: clean track for use in any app
- Export Plan: track + waypoints + no-go areas in GPX extensions
  (trails:planning namespace) for reimporting into the planner

Also:
- Add no-go area serialization to generateGpx (GPX extensions)
- Parse no-go areas from GPX extensions on import
- Initialize no-go areas in Yjs session from imported GPX
- Save to Journal now exports track only (consistent with Export Route)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/i18n/src/locales/de.ts

@@ -18,6 +18,8 @@ export default {
     newSession: "Neue Sitzung",
     saveRoute: "Route speichern",
     exportGpx: "GPX exportieren",
+    exportRoute: "Route exportieren",
+    exportPlan: "Plan exportieren",
     profile: "Profil",
     connecting: "Verbinde...",
     loadingMap: "Karte wird geladen...",

packages/i18n/src/locales/en.ts

@@ -18,6 +18,8 @@ export default {
     newSession: "New Session",
     saveRoute: "Save Route",
     exportGpx: "Export GPX",
+    exportRoute: "Export Route",
+    exportPlan: "Export Plan",
     profile: "Profile",
     connecting: "Connecting...",
     loadingMap: "Loading map...",