Upgrade to React 19, Tailwind 4, and new shadcn baseline (#153)

* Upgrade to React 19, Tailwind 4, and new shadcn baseline

Propagate changes from paranext-core upgrade-shadcn branch:
- Update package.json deps (React 19, TW4, @tailwindcss/postcss,
  @dreamsicle.io/stylelint-config-tailwindcss, tw-animate-css,
  shadcn@4.3.0, @fontsource-variable/ibm-plex-sans, lucide-react@1.8,
  eslint-plugin-react-hooks@5)
- Slim tailwind.config.ts (TW4 moves theme/colors/etc into CSS)
- postcss.config.ts uses @tailwindcss/postcss
- .stylelintrc.js uses @Dreamsicle config and ignores new TW4 at-rules
- src/tailwind.css rewritten for TW4: imports tailwindcss with prefix(tw),
  tw-animate-css, shadcn/tailwind.css, fontsource font; @theme inline,
  @custom-variant dark, oklch theme variables (light/dark/paratext-light/
  paratext-dark)
- web-view-resolve-webpack-plugin.ts: bind resolver.join to resolver

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

* Propagated override

* Added success color variable

* Rename success → success-foreground, add warning theme variables

- Rename CSS variable `--success` → `--success-foreground` (and the
  corresponding `--color-success` → `--color-success-foreground` in
  `@theme inline`) to align with shadcn's `*-foreground` naming.
- Add `--warning` and `--warning-foreground` (amber-400/amber-950 in
  light themes, amber-900/amber-50 in dark themes) plus their
  `--color-warning` / `--color-warning-foreground` entries in
  `@theme inline`. Pulled from
  https://ui.shadcn.com/docs/theming#adding-new-tokens.
- Add a CUSTOM "Theme variable policy" disclaimer at the top of the
  file reminding extension authors to prefer existing theme variables
  and to get UX approval before introducing new semantic colors.

* Fixed package-lock.json, audit fix

---------

Co-authored-by: Claude Code <noreply@anthropic.com>

Author: tjcouch-sil

.stylelintrc.js

@@ -4,7 +4,7 @@ module.exports = {
   extends: [
     'stylelint-config-recommended',
     'stylelint-config-sass-guidelines',
-    'stylelint-config-tailwindcss/scss',
+    '@dreamsicle.io/stylelint-config-tailwindcss',
   ],
   overrides: [
     {
@@ -29,7 +29,18 @@ module.exports = {
     'scss/at-rule-no-unknown': [
       true,
       {
-        ignoreAtRules: ['tailwind', 'apply', 'layer', 'screen', 'variants'],
+        ignoreAtRules: [
+          'tailwind',
+          'apply',
+          'layer',
+          'screen',
+          'variants',
+          'config',
+          'theme',
+          'plugin',
+          'source',
+          'custom-variant',
+        ],
       },
     ],
     'selector-max-compound-selectors': 4,