fix: scope zod@3.25.76 pin to @backstage/plugin-auth-node only

PR #4354 pinned `zod` globally to `3.25.76` via `resolutions` to fix a
duplicate-version conflict with `@backstage/plugin-auth-node`. That
global pin also forces `rulesync`'s nested `zod` dep to 3.25.76 — but
`rulesync@7.23.0` imports `zod/mini`, which only exists in `zod@4.3.6`.
Result: `yarn rulesync:generate` fails on every PR with
`ERR_PACKAGE_PATH_NOT_EXPORTED: Package subpath './mini' is not defined`.

Scope the resolution to `@backstage/plugin-auth-node/zod` so the
original Backstage conflict is still fixed while `rulesync` can keep
its `zod@4.3.6` nested under `node_modules/rulesync/node_modules/zod`.

Verified:
- Top-level `node_modules/zod`: 3.25.76 (Backstage uses `zod/v3`)
- `node_modules/rulesync/node_modules/zod`: 4.3.6 (has `./mini`)
- `yarn rulesync:generate` runs cleanly — "All files are up to date"

This can be reverted once backstage/backstage#33536
lands upstream, same as the original resolution.

Author: gustavolira

package.json

@@ -67,7 +67,7 @@
     "@types/react": "18.3.28",
     "@types/react-dom": "18.3.7",
     "refractor@npm:3.6.0/prismjs": "^1.30.0",
-    "zod": "3.25.76"
+    "@backstage/plugin-auth-node/zod": "3.25.76"
   },
   "jest": {
     "testTimeout": 20000

yarn.lock

@@ -40174,13 +40174,20 @@ __metadata:
   languageName: node
   linkType: hard
 
-"zod@npm:3.25.76":
+"zod@npm:3.25.76, zod@npm:^3.22.4, zod@npm:^3.25.76":
   version: 3.25.76
   resolution: "zod@npm:3.25.76"
   checksum: 10c0/5718ec35e3c40b600316c5b4c5e4976f7fee68151bc8f8d90ec18a469be9571f072e1bbaace10f1e85cf8892ea12d90821b200e980ab46916a6166a4260a983c
   languageName: node
   linkType: hard
 
+"zod@npm:4.3.6, zod@npm:^3.25 || ^4.0, zod@npm:^3.25.76 || ^4.0.0, zod@npm:^4.1.13":
+  version: 4.3.6
+  resolution: "zod@npm:4.3.6"
+  checksum: 10c0/860d25a81ab41d33aa25f8d0d07b091a04acb426e605f396227a796e9e800c44723ed96d0f53a512b57be3d1520f45bf69c0cb3b378a232a00787a2609625307
+  languageName: node
+  linkType: hard
+
 "zstd-codec@npm:^0.1.5":
   version: 0.1.5
   resolution: "zstd-codec@npm:0.1.5"