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-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "pinchchat",
-  "version": "1.64.1",
+  "version": "1.64.2",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "pinchchat",
-      "version": "1.64.1",
+      "version": "1.64.2",
       "license": "MIT",
       "dependencies": {
         "@tailwindcss/vite": "^4.1.18",