feat: verify context attestations via ES256/JWKS + rename client to appshell-crm

Proof #3 now supports the production asymmetric path, not just the dev shared secret.

- context-attestation.ts: PublicKeyResolverPort seam; verify() picks ES256 (JWKS by
  kid) when the client has a jwksUri, else HS256 (dev). signDevAttestationES256 helper.
- attestation-stores.ts: JwksPublicKeyResolver (jwks-rsa, one cached client per URI,
  refetch on rotation, fail-closed to NO_KEY).
- attestation.module.ts: inject the resolver into the verifier; dev-seed the client as
  clientType APPSHELL (it is the CRM browser-flow parent per the July-12 notes).
- rename the registered client crm-support-widget -> appshell-crm (the name reflects the
  attesting parent, not a widget).
- specs: ES256 (valid via JWKS, wrong key -> BAD_SIGNATURE, unknown kid -> NO_KEY, no
  resolver -> NO_KEY) + two stolen-token gate cases (wrong app binding -> APP_MISMATCH,
  wrong audience -> WRONG_AUDIENCE).

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

packages/iios-service/package.json

@@ -26,6 +26,7 @@
     "dotenv": "^16.4.7",
     "ioredis": "^5.11.1",
     "jsonwebtoken": "^9.0.3",
+    "jwks-rsa": "^4.1.0",
     "prisma": "^6.2.1",
     "reflect-metadata": "^0.2.2",
     "rxjs": "^7.8.2",