fix(GRO-666): leave staff.user_id NULL in seed so middleware can auto-link by email

The resolveStaffMiddleware auto-links on first API call when staff.user_id
IS NULL. Setting userId at seed time blocks this path since Better-Auth's
user.id is opaque and unknown pre-auth. Remove userId from all staff inserts
so the middleware can populate it on first authenticated call.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/db/src/seed.ts

@@ -399,7 +399,6 @@ async function seedKnownUsers() {
         name: adminName,
         email: adminEmail,
         oidcSub: adminEmail,
-        userId: adminEmail,
         role: "manager",
         isSuperUser: true,
         active: true,
@@ -426,7 +425,6 @@ async function seedKnownUsers() {
         name: "UAT Super User",
         email: "uat-super@groombook.dev",
         oidcSub: uatSuperOidcSub,
-        userId: uatSuperOidcSub,
         role: "manager",
         isSuperUser: true,
         active: true,
@@ -453,7 +451,6 @@ async function seedKnownUsers() {
         name: "UAT Staff Groomer",
         email: "uat-groomer@groombook.dev",
         oidcSub: uatStaffOidcSub,
-        userId: uatStaffOidcSub,
         role: "groomer",
         isSuperUser: false,
         active: true,
@@ -648,7 +645,6 @@ async function seed() {
         name: adminName,
         email: adminEmail,
         oidcSub: adminEmail,
-        userId: adminEmail,
         role: "manager",
         isSuperUser: true,
         active: true,