release(v4.8.1): SHADE_DISABLE_RATE_LIMIT env var for single-tenant deploys

Plumbing fix only — both createPrekeyRoutes and createInboxRoutes
already accepted disableRateLimit; standalone.ts just didn't read
the env. Now SHADE_DISABLE_RATE_LIMIT=1 turns off IP rate-limits on
every prekey + inbox route, with a WARN log on startup so operators
see it.

Single-tenant deployments only — multi-tenant relays must leave it
unset. Documented in docs/DEPLOYMENT.md.

Reported by Prism: ~6 pair attempts/hour from a single dev IP +
the sidecar's register call tripped the 5/hour REGISTER_LIMIT every
dev iteration.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/shade-transport-bridge/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@shade/transport-bridge",
-  "version": "4.8.0",
+  "version": "4.8.1",
   "type": "module",
   "main": "src/index.ts",
   "types": "src/index.ts",