feat: patient wallet — real Signing, encrypted share relay, import-from-app

Backend
- clinic Ed25519 signing key (services/signing.ts, routes/signing.ts,
  clinic_signing_keys table) — Settings → Signing is now real
- @noble wallet-crypto (lib/wallet-crypto.ts): ed25519 identity, base58check
  wallet numbers, sealed-box (x25519 + xchacha20poly1305)
- /wallet Socket.io relay namespace (challenge-signed device auth) forwarding
  only ciphertext; emitToWallet helper
- import-from-app flow (routes/patients-wallet.ts, services/wallet-share.ts):
  request-share → patient approval → decrypt + verify → review draft → commit
- temporary shares: patients.share_expires_at + 5-min auto-delete sweep; revoke

Frontend
- SigningPanel wired to live key/fingerprint/rotate + shared-records list
- "Import from a patient app" dialog (lib/signing.ts, import-from-wallet-dialog)
  reusing the draft-review path; temporary badge on the patient list

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/package-lock.json

@@ -13,6 +13,9 @@
         "@ai-sdk/google": "^3.0.82",
         "@ai-sdk/openai": "^3.0.71",
         "@ai-sdk/openai-compatible": "^2.0.50",
+        "@noble/ciphers": "^2.2.0",
+        "@noble/curves": "^2.2.0",
+        "@noble/hashes": "^2.2.0",
         "@types/multer": "^2.1.0",
         "ai": "^6.0.204",
         "better-auth": "^1.6.13",
@@ -2183,6 +2186,21 @@
         "url": "https://paulmillr.com/funding/"
       }
     },
+    "node_modules/@noble/curves": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/@noble/curves/-/curves-2.2.0.tgz",
+      "integrity": "sha512-T/BoHgFXirb0ENSPBquzX0rcjXeM6Lo892a2jlYJkqk83LqZx0l1Of7DzlKJ6jkpvMrkHSnAcgb5JegL8SeIkQ==",
+      "license": "MIT",
+      "dependencies": {
+        "@noble/hashes": "2.2.0"
+      },
+      "engines": {
+        "node": ">= 20.19.0"
+      },
+      "funding": {
+        "url": "https://paulmillr.com/funding/"
+      }
+    },
     "node_modules/@noble/hashes": {
       "version": "2.2.0",
       "resolved": "https://registry.npmjs.org/@noble/hashes/-/hashes-2.2.0.tgz",