chore: scaffold PYRE MVP monorepo (structure + docs)

pnpm + TypeScript workspace per design doc §13:
- apps/{web,api,worker} skeletons (Next.js 16, Fastify 5, BullMQ)
- packages/{core,solana,prometheus,db,config} (core has real types/DTOs;
  solana/prometheus are stubs)
- programs/pyre-core placeholder (future Anchor, v1.0)
- docs/: PYRE_MVP_DESIGN (canonical), ARCHITECTURE, SECURITY, TOKEN_CLASSIFICATION
- CLAUDE.md, README, .env.example (no private-key var by design)

Skeleton + docs only — no Solana/business logic yet. All workspaces typecheck clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/postcss.config.mjs

@@ -0,0 +1,8 @@
+/** Tailwind CSS v4 PostCSS setup. */
+const config = {
+  plugins: {
+    "@tailwindcss/postcss": {},
+  },
+};
+
+export default config;