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-transition/src/selection/index.js

@@ -0,0 +1,6 @@
+import {selection} from "d3-selection";
+import selection_interrupt from "./interrupt.js";
+import selection_transition from "./transition.js";
+
+selection.prototype.interrupt = selection_interrupt;
+selection.prototype.transition = selection_transition;

frontend/node_modules/d3-transition/src/selection/interrupt.js

@@ -0,0 +1,7 @@
+import interrupt from "../interrupt.js";
+
+export default function(name) {
+  return this.each(function() {
+    interrupt(this, name);
+  });
+}

frontend/node_modules/d3-transition/src/selection/transition.js

@@ -0,0 +1,42 @@
+import {Transition, newId} from "../transition/index.js";
+import schedule from "../transition/schedule.js";
+import {easeCubicInOut} from "d3-ease";
+import {now} from "d3-timer";
+
+var defaultTiming = {
+  time: null, // Set on use.
+  delay: 0,
+  duration: 250,
+  ease: easeCubicInOut
+};
+
+function inherit(node, id) {
+  var timing;
+  while (!(timing = node.__transition) || !(timing = timing[id])) {
+    if (!(node = node.parentNode)) {
+      throw new Error(`transition ${id} not found`);
+    }
+  }
+  return timing;
+}
+
+export default function(name) {
+  var id,
+      timing;
+
+  if (name instanceof Transition) {
+    id = name._id, name = name._name;
+  } else {
+    id = newId(), (timing = defaultTiming).time = now(), name = name == null ? null : name + "";
+  }
+
+  for (var groups = this._groups, m = groups.length, j = 0; j < m; ++j) {
+    for (var group = groups[j], n = group.length, node, i = 0; i < n; ++i) {
+      if (node = group[i]) {
+        schedule(node, name, id, i, group, timing || inherit(node, id));
+      }
+    }
+  }
+
+  return new Transition(groups, this._parents, name, id);
+}