feat: festival/series model with sub-events, cross-event sections, tab navigation, SectionsShiftsPanel extraction

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

apps/app/package.json

@@ -17,7 +17,6 @@
     "@casl/ability": "6.7.3",
     "@casl/vue": "2.2.2",
     "@floating-ui/dom": "1.6.8",
-    "@formkit/drag-and-drop": "0.1.6",
     "@sindresorhus/is": "7.1.0",
     "@tanstack/vue-query": "^5.95.2",
     "@tiptap/extension-highlight": "^2.27.1",
@@ -55,6 +54,7 @@
     "vue-router": "4.5.1",
     "vue3-apexcharts": "1.5.3",
     "vue3-perfect-scrollbar": "2.0.0",
+    "vuedraggable": "^4.1.0",
     "vuetify": "3.10.8",
     "webfontloader": "1.6.28",
     "zod": "3"