Add visual graph editor for entity interconnections

SVG-based node graph with ELK.js autolayout showing all 13 entity types
and their relationships. Features include:

- Pan/zoom canvas with bounds clamping and dead-zone click detection
- Interactive minimap with viewport rectangle, click-to-pan, drag-to-move,
  and dual resize handles (bottom-left/bottom-right)
- Movable toolbar with drag handle and inline zoom percentage indicator
- Entity-type SVG icons from Lucide icon set with subtype-specific overrides
- Command palette search (/) with keyboard navigation and fly-to
- Node selection with upstream/downstream chain highlighting
- Double-click to zoom-to-card, edit/delete overlay on hover
- Legend panel, orphan node detection, running state indicators
- Full i18n support with languageChanged re-render
- Catmull-Rom-to-cubic bezier edge routing for smooth curves

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

contexts/frontend.md

@@ -144,3 +144,15 @@ When adding **new tabs, sections, or major UI elements**, update the correspondi
 - In inline `<script>` blocks (where `t()` may not be available yet): use `window.t ? t('key') : 'fallback'`
 - In HTML templates: use `data-i18n="key"` for text content, `data-i18n-title="key"` for title attributes, `data-i18n-aria-label="key"` for aria-labels
 - Keys follow dotted namespace convention: `feature.context.description` (e.g. `device.error.brightness`, `calibration.saved`)
+
+### Dynamic content and language changes
+
+When a feature module generates HTML with baked-in `t()` calls (e.g., toolbar button titles, legend text), that content won't update when the user switches language. To handle this, listen for the `languageChanged` event and re-render:
+
+```javascript
+document.addEventListener('languageChanged', () => {
+    if (_initialized) _reRender();
+});
+```
+
+Static HTML using `data-i18n` attributes is handled automatically by the i18n system. Only dynamically generated HTML needs this pattern.