Add store settings page with location management

Company table gains address and logo_file_id columns. New store
settings API: GET/PATCH /store for company info, full CRUD for
/locations. Settings page shows store name, phone, email, address,
timezone with inline edit. Location cards with add/edit/delete.
Settings link in admin sidebar. Fixes leftover company_id on
location table and seed files.

packages/backend/src/db/seed.ts

@@ -26,7 +26,6 @@ async function seed() {
     .insert(locations)
     .values({
       id: DEV_LOCATION_ID,
-      companyId: DEV_COMPANY_ID,
       name: 'Main Store',
       address: {
         street: '123 Main St',