refactor: migrate project storage from IndexedDB to OPFS with folder-based structure

- Replace monolithic KGStorage with KGProjectStorage (OPFS) and KGConfigStorage (IndexedDB)
- Each project stored as folder: project.json + meta.json + media/
- Add KGConfigUpgrader with V1 upgrader to auto-migrate existing IndexedDB projects to OPFS
- Request persistent storage via navigator.storage.persist() to prevent browser eviction
- Show loading spinner during one-time migration
- Enforce safe project name characters (letters, numbers, space, hyphen, underscore, period, parens)
- Export projects as .kgstudio zip bundles instead of raw JSON
- Import supports .kgstudio bundles (with meta.json validation) and legacy JSON files
- Auto-deduplicate project names on import with (1), (2), etc. suffix
- Add OPFS shell debugger (pwd, ls, cd, cat, dl) accessible via KGDebugger.opfs()
- Add ESLint semi rule for consistent semicolons
- Delete KGStorage.ts — all logic absorbed by new storage classes
- Add jszip dependency for zip export/import

package.json

@@ -16,6 +16,7 @@
   "dependencies": {
     "class-transformer": "^0.5.1",
     "idb": "^8.0.3",
+    "jszip": "^3.10.1",
     "openai": "^6.33.0",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",