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>

backend/target/debug/.fingerprint/tokio-stream-5e950f9c1612441b/invoked.timestamp

@@ -0,0 +1 @@
+This file has an mtime of when this was started.

backend/target/debug/.fingerprint/tokio-stream-5e950f9c1612441b/lib-tokio_stream

@@ -0,0 +1 @@
+a0076c855c752b6f

backend/target/debug/.fingerprint/tokio-stream-5e950f9c1612441b/lib-tokio_stream.json

@@ -0,0 +1 @@
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