Various build shenenigans (#5)

This PR extends the build pipeline of the www service to support
locale-prefixed static builds (EN/RU) with build-time SSG output
injection, while also refactoring UI typography to a tokenized Tailwind
v4 @theme-driven approach.

Changes:

- Add build-time SSG plugin to @ermnvldmr/rsbuild-config and wire
multi-locale builds (/en/, /ru/) into services/www.
- Introduce new @ermnvldmr/i18n package (locale constants, path helpers,
keysets, pluralization) and apply it to www navigation/text.
- Refactor ui typography to a shared getTypographyClassNames utility +
Tailwind token definitions, with stl/cn updated for correct
Tailwind-merge behavior.

services/static/src/lib/core/createPage.tsx

@@ -22,6 +22,7 @@ export interface PageOptions {
  * ```
  */
 export function createPage(Component: React.ComponentType, options: PageOptions = {}): void {
+  if (typeof window === 'undefined') return; // SSG build context: skip DOM mounting
   const rootElement = document.getElementById('root');
 
   if (options.title) {