Address the 11 October test report findings

The initial test report (run before the pilot-readiness changes) raised
seven findings and a retest plan. This closes the ones still open.

- F-01: a business on its free trial may run 2 active branches whatever
  its tier, so an owner can try transfers and per-branch stock. Only
  active branches count towards any limit.
- F-06: owners can rename branches and deactivate/reactivate them from
  the Branches page. A branch can only be deactivated once it holds no
  stock and no active staff; its history stays in every report, and it
  leaves every picker.
- F-04: the Products page lists deactivated products under a toggle with
  Reactivate. Deactivating warns about stock still on hand, which stays
  on the Stock page so it can be transferred or counted out.
- F-05: products carry a unit (L, ml, kg, g, pcs, tray, pack) instead of
  everything being litres.
- CAT-12: product prices must be above zero and names are unique per
  business, ignoring case.
- F-03: a reversed report period is refused by the page and the API, and
  the page labels which period the cards show. Report dates are Nairobi
  business days.
- F-07: cost of goods sold is units sold x average buying price. Stock
  bought in the period is reported separately, with a cash surplus line,
  so unsold stock no longer shows as a loss.
- STA-04: staff and new branch managers can be invited with a one-time,
  7-day link; the person sets their own password. Managers can issue a
  new link for their own cashiers.
- OFF-02 / POS-02: the till shows each product's stock and deducts every
  sale immediately, online or offline; it warns before selling more than
  the recorded stock, and has a Clear sale button.
- npm run backfill:stock turns purchases recorded before the stock ledger
  into stock, so existing tenants (and the report's ZERRO fixtures) start
  from what they bought.

tests/retest-plan.test.ts runs the report's completion and retest plan
and checks every balance and total it predicts.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/api/users/[id]/route.ts

@@ -3,7 +3,7 @@ import { z } from "zod";
 import { isValidObjectId } from "mongoose";
 import { connectDb } from "@/lib/server/db";
 import { User } from "@/lib/server/models/User";
-import { Branch } from "@/lib/server/models/Branch";
+import { ACTIVE_BRANCH, Branch } from "@/lib/server/models/Branch";
 import { Business } from "@/lib/server/models/Business";
 import { UserSession } from "@/lib/server/models/UserSession";
 import { authorize, MANAGERS } from "@/lib/server/auth";
@@ -67,7 +67,7 @@ export async function PATCH(req: NextRequest, { params }: { params: { id: string
     if (target.role === "SUPER_ADMIN") {
       return NextResponse.json({ error: "Owner accounts are not tied to a branch" }, { status: 400 });
     }
-    const branch = await Branch.findOne({ _id: branchId, businessId: auth.businessId }).lean();
+    const branch = await Branch.findOne({ _id: branchId, businessId: auth.businessId, ...ACTIVE_BRANCH }).lean();
     if (!branch) return NextResponse.json({ error: "Branch not found in your business" }, { status: 404 });
     target.branchId = branch._id;
   }
@@ -82,5 +82,6 @@ export async function PATCH(req: NextRequest, { params }: { params: { id: string
 
   const obj = target.toObject() as unknown as Record<string, unknown>;
   delete obj.passwordHash;
+  delete obj.inviteTokenHash;
   return NextResponse.json({ user: obj });
 }