Add side panels, task selection, graph animation, and project docs

- Foldable left panel (user profile) and right panel (task details)
- Clicking a task in the list or graph node selects it and shows details
- Both views (task list + graph) always mounted via absolute inset-0 for
  correct canvas dimensions; tabs toggle visibility with opacity
- Graph node selection animation: other nodes repel outward (charge -600),
  then selected node smoothly slides to center (500ms cubic ease-out),
  then charge restores to -120 and graph stabilizes
- Graph re-fits on tab switch and panel resize via ResizeObserver
- Fix UUID string IDs throughout (backend returns UUIDs, not integers)
- Add TaskDetailPanel, UserPanel components
- Add CLAUDE.md project documentation

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

frontend/node_modules/autoprefixer/lib/hacks/placeholder.js

@@ -0,0 +1,33 @@
+let Selector = require('../selector')
+
+class Placeholder extends Selector {
+  /**
+   * Add old mozilla to possible prefixes
+   */
+  possible() {
+    return super.possible().concat(['-moz- old', '-ms- old'])
+  }
+
+  /**
+   * Return different selectors depend on prefix
+   */
+  prefixed(prefix) {
+    if (prefix === '-webkit-') {
+      return '::-webkit-input-placeholder'
+    }
+    if (prefix === '-ms-') {
+      return '::-ms-input-placeholder'
+    }
+    if (prefix === '-ms- old') {
+      return ':-ms-input-placeholder'
+    }
+    if (prefix === '-moz- old') {
+      return ':-moz-placeholder'
+    }
+    return `::${prefix}placeholder`
+  }
+}
+
+Placeholder.names = ['::placeholder']
+
+module.exports = Placeholder