feat(09-05): ProfileChannelsSection (Teams + ntfy + QR code) + qrcode.react install

- Create ProfileChannelsSection.tsx with Teams + ntfy sub-sections
- Teams: URL input, inline 400 error (teamsError), save/clear buttons, inline test result
- ntfy: mint-on-first-save (State A → State B), QR code via QRCodeSVG, subscribe link
- ntfy: advanced disclosure with custom topic input + inline 400 error (customTopicError)
- ntfy: test-now and remove buttons
- Install qrcode.react ^4.2.0 (node_modules + package.json + package-lock.json updated)
- Delete ProfileChannelsSectionPlaceholder.tsx (replaced by real component)
- Update app/mobile/profile/page.tsx import to ProfileChannelsSection (not Placeholder)

package-lock.json

@@ -43,6 +43,7 @@
         "node-cron": "^4.2.1",
         "nodemailer": "^7.0.12",
         "pg": "^8.11.0",
+        "qrcode.react": "^4.2.0",
         "radix-ui": "^1.4.3",
         "react": "19.2.3",
         "react-day-picker": "^9.13.0",
@@ -14789,6 +14790,15 @@
         "node": ">=6"
       }
     },
+    "node_modules/qrcode.react": {
+      "version": "4.2.0",
+      "resolved": "https://registry.npmjs.org/qrcode.react/-/qrcode.react-4.2.0.tgz",
+      "integrity": "sha512-QpgqWi8rD9DsS9EP3z7BT+5lY5SFhsqGjpgW5DY/i3mK4M9DTBNz3ErMi8BWYEfI3L0d8GIbGmcdFAS1uIRGjA==",
+      "license": "ISC",
+      "peerDependencies": {
+        "react": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
     "node_modules/qs": {
       "version": "6.15.1",
       "resolved": "https://registry.npmjs.org/qs/-/qs-6.15.1.tgz",