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-server/tests/rate-limit.test.ts

@@ -102,6 +102,48 @@ describe('Rate limiting integration with routes', () => {
     expect(results.filter((s) => s === 429).length).toBeGreaterThanOrEqual(1);
   });
 
+  // V4.8.1 — `SHADE_DISABLE_RATE_LIMIT=1` in standalone.ts is plumbed
+  // through to `createPrekeyServer({ disableRateLimit })`. This test
+  // covers the "what happens when the flag is true" path; the env-var
+  // → option conversion in standalone.ts is a one-liner verified by
+  // inspection.
+  test('register endpoint allows >5/hour from a single IP when disableRateLimit is set', async () => {
+    const app = createPrekeyServer({
+      crypto,
+      store: new MemoryPrekeyStore(),
+      disableRateLimit: true,
+    });
+
+    async function doRegister(addressSuffix: number) {
+      const identity = await generateIdentityKeyPair(crypto);
+      const body: any = {
+        address: `user${addressSuffix}`,
+        identitySigningKey: Buffer.from(identity.signingPublicKey).toString('base64'),
+        identityDHKey: Buffer.from(identity.dhPublicKey).toString('base64'),
+        signedPreKey: {
+          keyId: 1,
+          publicKey: Buffer.from(crypto.randomBytes(32)).toString('base64'),
+          signature: Buffer.from(crypto.randomBytes(64)).toString('base64'),
+        },
+      };
+      const signed = await signPayload(crypto, identity.signingPrivateKey, body);
+      return app.request('/v1/keys/register', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json', 'x-forwarded-for': '203.0.113.1' },
+        body: JSON.stringify(signed),
+      });
+    }
+
+    const results: number[] = [];
+    for (let i = 0; i < 12; i++) {
+      const res = await doRegister(i);
+      results.push(res.status);
+    }
+    // No 429 anywhere — the limit is OFF.
+    expect(results.filter((s) => s === 429).length).toBe(0);
+    expect(results.filter((s) => s === 200).length).toBe(12);
+  });
+
   test('rate limit returns Retry-After header', async () => {
     const app = createPrekeyServer({ crypto, store: new MemoryPrekeyStore() });