Add guided tour feature with Driver.js

- Install driver.js package for lightweight product tours
- Create GuidedTour component with bilingual tour steps (Chinese/English)
- Create TourPromptModal to ask users if they want a tour after welcome
- Add data-tour attributes to Toolbar, FilePanel, PedigreeCanvas, PropertyPanel
- Tour covers: file operations, adding persons, canvas usage, relationships,
  editing properties, and exporting

Tour flow:
1. First visit: Welcome Modal → Tour Prompt Modal → Start tour or skip
2. Subsequent visits: No modals shown

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

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

package.json

@@ -11,6 +11,7 @@
   },
   "dependencies": {
     "d3": "^7.9.0",
+    "driver.js": "^1.4.0",
     "html-to-image": "^1.11.13",
     "react": "^19.2.0",
     "react-dom": "^19.2.0",