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/release/.fingerprint/rustls-beff905dffd3398f/lib-rustls.json

@@ -0,0 +1 @@
+{"rustc":5391851738765093524,"features":"[\"dangerous_configuration\", \"tls12\"]","declared_features":"[\"dangerous_configuration\", \"default\", \"log\", \"logging\", \"quic\", \"read_buf\", \"rustversion\", \"secret_extraction\", \"tls12\"]","target":4244986261372225136,"profile":1369601567987815722,"path":11140413430061255311,"deps":[[1584044471721254096,"sct",false,15599350888208664414],[5491919304041016563,"ring",false,4888417185334676516],[8804456559385901708,"webpki",false,1540306455228616746],[11295624341523567602,"build_script_build",false,10625840299342008713]],"local":[{"CheckDepInfo":{"dep_info":"release/.fingerprint/rustls-beff905dffd3398f/dep-lib-rustls","checksum":false}}],"rustflags":[],"config":8247474407144887393,"compile_kind":0}