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.

packages/ui/.config/vitest/setup.ts

@@ -22,3 +22,19 @@ Object.defineProperty(window, 'matchMedia', {
     dispatchEvent: vi.fn(),
   })),
 });
+
+// jsdom sometimes does not expose localStorage.clear(); provide a functional polyfill
+if (typeof window.localStorage.clear !== 'function') {
+  const store = new Map<string, string>();
+  Object.defineProperty(window, 'localStorage', {
+    configurable: true,
+    value: {
+      getItem: (key: string): string | null => store.get(key) ?? null,
+      setItem: (key: string, value: string): void => { store.set(key, value); },
+      removeItem: (key: string): void => { store.delete(key); },
+      clear: (): void => { store.clear(); },
+      key: (index: number): string | null => [...store.keys()][index] ?? null,
+      get length(): number { return store.size; },
+    },
+  });
+}