bug(macos): Mac App Store USB printing via CUPS/IPP (needs device repro) #1347

Parent: #830 (chat leftovers). Needs device repro. platform: macOS (Mac App Store). Verified against main @ 8e39053.

Report

USB receipt printers do not work on the Mac App Store build.

What we know

• The MAS build routes USB printing through loopback IPP to CUPS, not raw USB: main/printers/thermal.ts isMasBuild (~L306, L358) leads to printViaLocalIpp (main/printers/ipp-client.ts). Added in fix: MAS USB printer support, order-number sanitization, cash-drawer settings #640 (5 Sep). No changes since 6 Sep.
• build/entitlements.mas.plist has print, network.client and network.server, but no USB device entitlement. This is by design, since CUPS owns the device.
• No test covers ipp-client.ts / printViaLocalIpp, and docs/printers.md does not explain the MAS requirement (the printer must be added in macOS System Settings > Printers as a raw/generic queue).

Steps

1. On the MAS build, add a USB ESC/POS printer in macOS Printers (Generic / raw). Select it in FloCafe and print a test receipt.
2. Capture the FloCafe diagnostics output and the CUPS log (/var/log/cups/error_log).
3. Try with the printer not added to CUPS, and confirm the error message tells the user what to do.

Acceptance

• Repro result recorded here.
• Unit tests for ipp-client.ts (request building, error mapping).
• A clear in-app error when no CUPS queue exists.
• The MAS USB setup documented (docs.flopos.com printers page).