feat: QR pairing for wallet import (backend + website)

- Backend: nullable wallet_number on wallet_share_requests (migration 0029);
  createPairingRequest + POST /api/patients/wallet/pair; applyShareResponse
  binds the authenticated wallet on QR (pairing) requests
- Frontend: Import dialog gains a "Show QR" mode rendering a temetro-pair QR
  (react-qr-code) the patient scans; requestWalletPairing helper; i18n keys

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

frontend/package-lock.json

@@ -55,6 +55,7 @@
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         "react-i18next": "^17.0.8",
         "react-jsx-parser": "^2.4.1",
+        "react-qr-code": "^2.2.0",
         "shadcn": "^4.8.3",
         "shiki": "^4.1.0",
         "socket.io-client": "^4.8.3",
@@ -10580,7 +10581,6 @@
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-      "dev": true,
       "license": "MIT",
       "dependencies": {
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@@ -12805,7 +12805,6 @@
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-      "dev": true,
       "license": "MIT",
       "dependencies": {
         "loose-envify": "^1.4.0",
@@ -12985,6 +12984,12 @@
         "node": ">=6"
       }
     },
+    "node_modules/qrcode-generator": {
+      "version": "2.0.4",
+      "resolved": "https://registry.npmjs.org/qrcode-generator/-/qrcode-generator-2.0.4.tgz",
+      "integrity": "sha512-mZSiP6RnbHl4xL2Ap5HfkjLnmxfKcPWpWe/c+5XxCuetEenqmNFf1FH/ftXPCtFG5/TDobjsjz6sSNL0Sr8Z9g==",
+      "license": "MIT"
+    },
     "node_modules/qs": {
       "version": "6.15.2",
       "resolved": "https://registry.npmjs.org/qs/-/qs-6.15.2.tgz",
@@ -13122,7 +13127,6 @@
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-      "dev": true,
       "license": "MIT"
     },
     "node_modules/react-jsx-parser": {
@@ -13167,6 +13171,19 @@
         "@types/react": "^18.0.0"
       }
     },
+    "node_modules/react-qr-code": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/react-qr-code/-/react-qr-code-2.2.0.tgz",
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+      "license": "MIT",
+      "dependencies": {
+        "prop-types": "^15.8.1",
+        "qrcode-generator": "^2.0.4"
+      },
+      "peerDependencies": {
+        "react": "*"
+      }
+    },
     "node_modules/react-remove-scroll": {
       "version": "2.7.2",
       "resolved": "https://registry.npmjs.org/react-remove-scroll/-/react-remove-scroll-2.7.2.tgz",