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/d3-ease/src/sin.js

@@ -0,0 +1,14 @@
+var pi = Math.PI,
+    halfPi = pi / 2;
+
+export function sinIn(t) {
+  return (+t === 1) ? 1 : 1 - Math.cos(t * halfPi);
+}
+
+export function sinOut(t) {
+  return Math.sin(t * halfPi);
+}
+
+export function sinInOut(t) {
+  return (1 - Math.cos(pi * t)) / 2;
+}