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>

packages/db/migrations/README.md

@@ -0,0 +1,15 @@
+# Migrations
+
+SQL migrations for the PYRE PostgreSQL database.
+
+**Empty for now** (skeleton). Migration files and a runner will be added here.
+
+## Convention (TODO)
+
+- One forward migration per file, ordered/timestamped (e.g.
+  `0001_init.sql`, `0002_<change>.sql`).
+- The first migration creates the initial MVP tables listed in the package
+  README (§15): `wallet_scans`, `token_accounts`, `cleanup_receipts`,
+  `prometheus_generations`, `spawn_records`.
+- A migration runner (in `@pyre/db`) applies pending migrations against
+  `DATABASE_URL`.