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/postcss-js/README.md

@@ -0,0 +1,22 @@
+# PostCSS JS
+
+<img align="right" width="135" height="95"
+     title="Philosopher’s stone, logo of PostCSS"
+     src="https://postcss.org/logo-leftp.svg">
+
+[PostCSS] for CSS-in-JS and styles in JS objects.
+
+For example, to use [Stylelint] or [RTLCSS] plugins in your workflow.
+
+<a href="https://evilmartians.com/?utm_source=postcss-js">
+  <img src="https://evilmartians.com/badges/sponsored-by-evil-martians.svg"
+       alt="Sponsored by Evil Martians" width="236" height="54">
+</a>
+
+[Stylelint]: https://github.com/stylelint/stylelint
+[PostCSS]:   https://github.com/postcss/postcss
+[RTLCSS]:    https://github.com/MohammadYounes/rtlcss
+
+
+## Docs
+Read full docs **[here](https://github.com/postcss/postcss-js#readme)**.