[grade=B urn:ump:bbfbsfru4nizg75wcxum7mwzhie6txhr22hw6jvz36wiihmgzmlq] P7 people store: dedupe upsert by providerUserId

Dogfood finding #3: upsertPerson resolved existing records by id only.
The wizard upserts a bootstrap admin AFTER a provider sync has already
created a person for the same Tailscale user (no id passed), so the same
providerUserId was duplicated into two records. Resolve existing by
providerUserId when no id is given; bootstrap Admin group + protectedAt are
preserved on the merge. New regression test; full suite 3414/3414.

dashcaddy-api/src/security/network-people-store.js

@@ -180,7 +180,17 @@ function createPeopleStore(opts = {}) {
   function upsertPerson(input = {}) {
     return _enqueue(() => {
       const data = _load();
-      const existing = input.id ? data.people[input.id] : null;
+      // Resolve the existing record by id when given, else by providerUserId
+      // (dogfood finding 2026-10-04: the wizard upserts a person AFTER a
+      // provider sync already created one for the same Tailscale user with no
+      // id — without this lookup the same providerUserId was duplicated).
+      const existing = input.id
+        ? data.people[input.id]
+        : (input.providerUserId
+            ? Object.values(data.people).find(
+                (p) => p.providerUserId && p.providerUserId === input.providerUserId
+              ) || null
+            : null);
       const isFirst = Object.keys(data.people).length === 0;
 
       const id = existing ? existing.id : (input.id || crypto.randomUUID());