feat(10-02): add first-login-wins is_admin bootstrap in upsertUser (D-01)

- zero-admin COUNT check before INSERT: first user gets is_admin=true
- subsequent users (admin already exists) get is_admin=false
- existing-user early-return path unchanged (is_admin not modified)
- Phase-12 hook comment: tighten to first login after app_config.setup_complete
- adds 'import { sql }' from drizzle-orm

apps/api/src/auth/user.ts

@@ -8,7 +8,7 @@
  * Source: RESEARCH.md § "User upsert with color assignment"
  */
 
-import { and, eq } from 'drizzle-orm';
+import { and, eq, sql } from 'drizzle-orm';
 import { db } from '../db/client.js';
 import { users } from '../db/schema.js';
 
@@ -109,7 +109,20 @@ export async function upsertUser(oidcIss: string, oidcSub: string, displayName?:
     COLOR_PALETTE.find((c) => !usedColors.has(c)) ??
     COLOR_PALETTE[usedColors.size % COLOR_PALETTE.length];
 
-  // 3. Insert new user row
+  // 3. First-login-wins is_admin bootstrap (D-01).
+  //    When zero admins currently exist, the first new user becomes admin.
+  //    Phase 12 will tighten this to: first user after app_config.setup_complete.
+  //    Until then, "first user when zero admins exist" is the bootstrap condition.
+  //    This hook reads cleanly: Phase 12 adds a setup_complete check before the
+  //    COUNT, so only first login AFTER setup is flagged — no restructuring needed.
+  const [{ count }] = await db
+    .select({ count: sql<number>`COUNT(*)` })
+    .from(users)
+    .where(eq(users.isAdmin, true))
+    .limit(1);
+  const shouldBeAdmin = Number(count) === 0;
+
+  // 4. Insert new user row
   // mysql2 has no RETURNING clause — use $returningId() then re-select
   const [inserted] = await db
     .insert(users)
@@ -118,10 +131,11 @@ export async function upsertUser(oidcIss: string, oidcSub: string, displayName?:
       oidcSub,
       displayName: displayName ?? null,
       color,
+      isAdmin: shouldBeAdmin,
     })
     .$returningId();
 
-  // 4. Re-select to return the full typed row
+  // 5. Re-select to return the full typed row
   const [newUser] = await db.select().from(users).where(eq(users.id, inserted.id)).limit(1);
 
   return newUser;