Add on-demand CSS: registry, pre-computed component classes, header compression

- Parse tw.css into per-class lookup registry at startup
- Pre-scan component CSS classes at registration time (avoid per-request regex)
- Compress SX-Css header: 8-char hash replaces full class list (LRU cache)
- Add ;@css comment annotation for dynamically constructed class names
- Safelist bg-sky-{100..400} in Tailwind config for menu-row-sx dynamic shades
- Client sends/receives hash, falls back gracefully on cache miss

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/static/styles/tailwind.config.js

@@ -0,0 +1,40 @@
+/** @type {import('tailwindcss').Config} */
+module.exports = {
+  safelist: [
+    // ~menu-row-sx builds bg-{colour}-{shade} dynamically via (str ...)
+    // Levels 1–4 produce shades 400–100 (level 5+ yields 0 or negative = no match)
+    { pattern: /^bg-sky-(100|200|300|400)$/ },
+  ],
+  content: [
+    '/root/rose-ash/shared/sx/templates/**/*.sx',
+    '/root/rose-ash/shared/browser/templates/**/*.html',
+    '/root/rose-ash/blog/sx/**/*.sx',
+    '/root/rose-ash/blog/browser/templates/**/*.html',
+    '/root/rose-ash/market/sx/**/*.sx',
+    '/root/rose-ash/market/browser/templates/**/*.html',
+    '/root/rose-ash/cart/sx/**/*.sx',
+    '/root/rose-ash/cart/browser/templates/**/*.html',
+    '/root/rose-ash/events/sx/**/*.sx',
+    '/root/rose-ash/events/browser/templates/**/*.html',
+    '/root/rose-ash/federation/sx/**/*.sx',
+    '/root/rose-ash/federation/browser/templates/**/*.html',
+    '/root/rose-ash/account/sx/**/*.sx',
+    '/root/rose-ash/account/browser/templates/**/*.html',
+    '/root/rose-ash/orders/sx/**/*.sx',
+    '/root/rose-ash/orders/browser/templates/**/*.html',
+    '/root/rose-ash/shared/sx/helpers.py',
+    '/root/rose-ash/blog/sx/sx_components.py',
+    '/root/rose-ash/market/sx/sx_components.py',
+    '/root/rose-ash/cart/sx/sx_components.py',
+    '/root/rose-ash/events/sx/sx_components.py',
+    '/root/rose-ash/federation/sx/sx_components.py',
+    '/root/rose-ash/account/sx/sx_components.py',
+    '/root/rose-ash/orders/sx/sx_components.py',
+  ],
+  theme: {
+    extend: {},
+  },
+  plugins: [
+    require('@tailwindcss/typography'),
+  ],
+}