Add proper PDF support for DreamTalk media

- Enable PDF file drops in EditNode3D, ProtoNode3D, SearchNode3D, and DreamspaceCanvas
- Add react-pdf library with bundled PDF.js worker for Electron/Obsidian compatibility
- Create PDFPreview component that renders first page as thumbnail
- Update DreamTalkSide and DreamSong to use PDFPreview instead of iframe
- Fix pre-existing lint errors (crypto -> globalThis.crypto)
- Make VaultService.getFullPath() public for external file operations

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: ProjectLiminality

package-lock.json

@@ -60,6 +60,7 @@
     "marked": "^16.4.1",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",
+    "react-pdf": "^10.2.0",
     "three": "^0.178.0",
     "uuid": "^11.0.5",
     "zustand": "^5.0.6"