feat(GRO-1445): provision Better-Auth credential accounts in seed.ts

GRO-1325 was marked done but never implemented. This adds the missing
Better-Auth user + account seeding for UAT email+password logins.

For each SEED_UAT_*_PASSWORD env var present, the seed now:
1. Creates (or links to existing) a Better-Auth user record with
   emailVerified: true
2. Creates a credential account with providerId: "credential"
   and a bcrypt-hashed password (using better-auth/crypto)
3. Links the staff record to the Better-Auth user via userId

Idempotent: skips user/account creation if already seeded.

Updated UAT_PLAYBOOK.md §4.1 — TC-API-1.4 through 1.9 now reference
the new seed provisioning (GRO-1325 was the missing piece).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

packages/db/package.json

@@ -25,6 +25,7 @@
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {
+    "better-auth": "^1.5.6",
     "drizzle-orm": "^0.38.4",
     "postgres": "^3.4.5"
   },

packages/db/src/seed.ts

@@ -18,7 +18,7 @@
 
 import postgres from "postgres";
 import { drizzle } from "drizzle-orm/postgres-js";
-import { eq, sql } from "drizzle-orm";
+import { eq, and, sql } from "drizzle-orm";
 import * as schema from "./schema.js";
 
 // ── Seed profile configuration ─────────────────────────────────────────────
@@ -490,6 +490,90 @@ async function seedKnownUsers() {
     }
   }
 
+  // ── Better-Auth email+password credentials for UAT accounts ──────────────────
+  // Provisions Better-Auth user + account records so UAT testers can log in
+  // via email+password (POST /api/auth/sign-in/email) instead of Authentik SSO.
+  const uatPasswordAccounts = [
+    { email: "uat-super@groombook.dev", name: "UAT Super User", passwordEnv: "SEED_UAT_SUPER_PASSWORD", staffEmail: "uat-super@groombook.dev" },
+    { email: "uat-groomer@groombook.dev", name: "UAT Staff Groomer", passwordEnv: "SEED_UAT_GROOMER_PASSWORD", staffEmail: "uat-groomer@groombook.dev" },
+    { email: "uat-customer@groombook.dev", name: "UAT Customer", passwordEnv: "SEED_UAT_CUSTOMER_PASSWORD", staffEmail: null },
+    { email: "uat-tester@groombook.dev", name: "UAT Tester", passwordEnv: "SEED_UAT_TESTER_PASSWORD", staffEmail: "uat-tester@groombook.dev" },
+  ];
+
+  for (const acct of uatPasswordAccounts) {
+    const password = process.env[acct.passwordEnv];
+    if (!password) {
+      console.warn(`⚠ Skipping ${acct.email} — ${acct.passwordEnv} not set`);
+      continue;
+    }
+
+    // 1. Find or create the Better-Auth user
+    const [existingUser] = await db
+      .select()
+      .from(schema.user)
+      .where(eq(schema.user.email, acct.email))
+      .limit(1);
+
+    let userId: string;
+    if (existingUser) {
+      userId = existingUser.id;
+      console.log(`✓ Better-Auth user '${acct.name}' already exists — skipping user creation`);
+    } else {
+      userId = uuid();
+      await db.insert(schema.user).values({
+        id: userId,
+        name: acct.name,
+        email: acct.email,
+        emailVerified: true,
+      });
+      console.log(`✓ Created Better-Auth user '${acct.name}' (${acct.email})`);
+    }
+
+    // 2. Check if credential account already exists
+    const [existingAccount] = await db
+      .select()
+      .from(schema.account)
+      .where(and(
+        eq(schema.account.userId, userId),
+        eq(schema.account.providerId, "credential")
+      ))
+      .limit(1);
+
+    if (existingAccount) {
+      console.log(`✓ Credential account for '${acct.email}' already exists — skipping`);
+    } else {
+      // Use Better-Auth's own hashPassword so the hash format matches what
+      // better-auth validates at sign-in time.
+      // better-auth/crypto uses: N=16384, r=16, p=1, dkLen=64.
+      const { hashPassword } = await import("better-auth/crypto");
+      const passwordHash = await hashPassword(password);
+
+      await db.insert(schema.account).values({
+        id: uuid(),
+        accountId: userId,
+        providerId: "credential",
+        userId,
+        password: passwordHash,
+      });
+      console.log(`✓ Created credential account for '${acct.email}'`);
+    }
+
+    // 3. Link staff record to Better-Auth user (for accounts that have staff records)
+    if (acct.staffEmail) {
+      const [existingStaff] = await db
+        .select()
+        .from(schema.staff)
+        .where(eq(schema.staff.email, acct.staffEmail))
+        .limit(1);
+      if (existingStaff && !existingStaff.userId) {
+        await db.update(schema.staff)
+          .set({ userId })
+          .where(eq(schema.staff.id, existingStaff.id));
+        console.log(`✓ Linked staff '${acct.staffEmail}' → Better-Auth user`);
+      }
+    }
+  }
+
   // ── Services: idempotent upsert using name as unique key ─────────────────────
   // UNIQUE constraint on services.name (migration 0020) must exist first.
   // Uses b0000001-... IDs to match main seed servicesDef for same-named services.