chore: upgrade ui and docs frontend dependencies to latest

ui: Vite 8, vue-tsc 3, TypeScript 6, @vitejs/plugin-vue 6, vis-network 10,
vis-data 8, FontAwesome 7, @types/node 25. docs: Vite 8, plugin-vue 6.
Both migrated to Tailwind CSS v4.

- Tailwind v3 -> v4: @import "tailwindcss" with @theme/@config, switch to
  @tailwindcss/postcss, drop autoprefixer (bundled via Lightning CSS).
- docs: move theme into @theme, delete tailwind.config.js, remove stale
  pnpm-lock.yaml (npm/package-lock.json is authoritative).
- ui: TypeScript 6 removes deprecated tsconfig baseUrl; no code changes
  needed for vis-network 10 / FontAwesome 7.
- Bump CI Node 20 -> 22 (Vite 8 requires Node ^20.19 || >=22.12).

0 npm audit vulnerabilities; ui type-check and both production builds pass.

.github/workflows/release.yaml

@@ -20,7 +20,7 @@ jobs:
         with:
             go-version: ">=1.24"
             node-enabled: true
-            node-version: "20"
+            node-version: "22"
             node-build-script: "cd ui && npm ci && npm run build"
             node-cache-dependency-path: "ui/package-lock.json"
             node-output-path: "ui/dist"

.github/workflows/static.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Setup Node.js
         uses: actions/setup-node@v4
         with:
-          node-version: '20'
+          node-version: '22'
           cache: 'npm'
           cache-dependency-path: 'docs/package-lock.json'