fix: revert @types/node to v20 to match production Node version

Production server (vmi2736502) uses Node v20.20.0, not v22.
@types/node must match the lowest Node version we support.

Changed:
- @types/node: ^22.12.5 → ^20.19.33

Local dev may use Node 22, but types must be compatible with
production Node 20 to avoid runtime errors from missing APIs.

https://claude.ai/code/session_015R3U3kiprQiNTTNNt31Sg6

yarn.lock

@@ -2323,6 +2323,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@types/node@npm:^20.19.33":
+  version: 20.19.33
+  resolution: "@types/node@npm:20.19.33"
+  dependencies:
+    undici-types: "npm:~6.21.0"
+  checksum: 10c0/a1a6234a2b6fa577fbb1ccc471e5e54a79c6e1a51be10a67b034461b752a50017854810e943494f20b3c3c6d14df84c93757e0a2ec57aa81c830d6faeab72cf2
+  languageName: node
+  linkType: hard
+
 "@types/node@npm:^22.0.0":
   version: 22.19.7
   resolution: "@types/node@npm:22.19.7"
@@ -2332,15 +2341,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@types/node@npm:^22.12.5":
-  version: 22.19.11
-  resolution: "@types/node@npm:22.19.11"
-  dependencies:
-    undici-types: "npm:~6.21.0"
-  checksum: 10c0/4b274acf27ec31aa83b50ef22088f83c783e6bcd7dcb40b4834f64f44868b6bf68725214220f15a0c776928f7c0f7f26f03c05cd5868f0526340af3f4af4b58b
-  languageName: node
-  linkType: hard
-
 "@types/normalize-package-data@npm:^2.4.4":
   version: 2.4.4
   resolution: "@types/normalize-package-data@npm:2.4.4"
@@ -3085,7 +3085,7 @@ __metadata:
     "@eslint/js": "npm:^9.31.0"
     "@hapi/boom": "npm:^10.0.1"
     "@types/jest": "npm:^30.0.0"
-    "@types/node": "npm:^22.12.5"
+    "@types/node": "npm:^20.19.33"
     "@types/ws": "npm:^8.0.0"
     "@typescript-eslint/eslint-plugin": "npm:^8.55.0"
     "@typescript-eslint/parser": "npm:^8.55.0"