feat: device identity for OpenClaw 2026.2.14+ pairing (#6)

- Generate Ed25519 keypair via Web Crypto API
- Persist keypair in IndexedDB (survives page reloads)
- Sign connect payload with device private key
- Include device object in connect params (id, publicKey, signature, signedAt)
- Handle NOT_PAIRED error with 'pairing' connection status
- Show pairing-pending banner with instructions to run openclaw devices approve
- Extract nonce from connect.challenge for v2 payload signing
- Add i18n translations for pairing banner in all 8 languages

Closes #6

package.json

@@ -1,6 +1,6 @@
 {
   "name": "pinchchat",
-  "version": "1.64.1",
+  "version": "1.64.2",
   "description": "A sleek, dark-themed webchat UI for OpenClaw — monitor sessions, stream responses, and inspect tool calls in real-time.",
   "type": "module",
   "repository": {