build(ui): add Tailwind v4 + daisyUI 5 pipeline

daisyUI is an npm plugin, so the standalone Tailwind CLI can't load it; this
adds a real build. Themes are configured as `light --default, dark
--prefersdark`, so dark follows the OS with no JavaScript, and an explicit
data-theme (set by the toggle) overrides it.

The built CSS is committed, so `uv run manage.py runserver` remains all a
Python dev needs; `npm run watch` is only for those touching styles.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -376,4 +376,6 @@ poetry.toml
 # LSP config files
 pyrightconfig.json
 
-# End of https://www.toptal.com/developers/gitignore/api/python,pycharm,django%
+# End of https://www.toptal.com/developers/gitignore/api/python,pycharm,django%
+# Node
+node_modules/