feat(hardening): M-Hard 6 + 7 — PostgreSQL backend + production server infra

M-Hard 6: PostgreSQL Storage Backend
- @shade/storage-postgres with PostgresStorage + PostgresPrekeyStore
- Drizzle-style raw SQL ensureClientTables / ensurePrekeyServerTables
- All tables prefixed `shade_` to avoid collisions in shared databases
- DELETE ... FOR UPDATE SKIP LOCKED for concurrent OTPK consumption
- Tests skip gracefully without SHADE_TEST_PG_URL, run against real PG when set

M-Hard 7: Production Server Infrastructure
- Structured JSON logger (logger.ts) — SHADE_LOG_LEVEL configurable
- Health endpoints (/health, /healthz, /ready) — Kubernetes-friendly
- Prometheus metrics (/metrics) — counters, histograms, middleware
- Graceful shutdown with SIGTERM/SIGINT handlers + store close
- Production Dockerfile with non-root user, healthcheck, multi-stage build
- docker-compose.yml example for Dokploy with optional PostgreSQL

193 tests passing, 0 failures.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/shade-storage-postgres/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "@shade/storage-postgres",
+  "version": "0.1.0",
+  "type": "module",
+  "main": "src/index.ts",
+  "types": "src/index.ts",
+  "dependencies": {
+    "@shade/core": "workspace:*",
+    "@shade/server": "workspace:*",
+    "drizzle-orm": "^0.45.2",
+    "postgres": "^3.4.9"
+  },
+  "devDependencies": {
+    "@shade/crypto-web": "workspace:*"
+  }
+}