v1.33.0 -- Manufacturer part number, cycle-count duplicate guard

Manufacturer part number on the item master, and a cycle count that can no longer double-count itself.

Added

Manufacturer part number on items (#438). Items carry an MPN alongside the SKU and UPC: the manufacturer's own catalogue number, used to match an arriving shipment line back to what was ordered when the SKU and UPC are not enough on their own. Migration 079 adds items.mpn, nullable and deliberately not unique, since one MPN can legitimately map to several SKUs (kits, re-packs, reseller renames) and is shared across manufacturers; ix_items_mpn mirrors ix_items_upc for lookup. The field is surfaced through item read, create and update, the CSV import schema, PO lines and receiving, and item search matches on it the way it matches on UPC. The Items, Purchase Order and Receiving views show it, and the PO line table grows UPC and MPN columns, neither of which it carried before. The inbound mapping can populate it where the sending system supplies one.

Fixed

Duplicate cycle-count lines from a double-submitted count (#439). A cycle count is scoped to a single bin, so each item should appear on exactly one line, but nothing enforced it. The mobile SUBMIT button could fire twice and submit_cycle_count re-checked status without locking the count row, so the second call re-ran the whole submit and re-INSERTed every "unexpected" line. Snapshot lines were spared because they UPDATE by count_line_id, but the unexpected lines duplicated, became duplicate PENDING inventory_adjustments, and approval then applied each variance as its own delta, double-counting on-hand.

Four layers now hold the invariant rather than relying on any one of them: the submit locks the count row and re-checks status under that lock; the unexpected-line write is idempotent per (count_id, item_id) and the create-time snapshot is aggregated per item; UNIQUE(count_id, item_id) is the structural backstop; and the mobile submit button disables itself while a submit is in flight, removing the common trigger at the source.

Migrations

079 items_mpn: adds mpn VARCHAR(64) to items plus ix_items_mpn. Nullable, not unique.

080 cycle_count_lines_unique: adds UNIQUE(count_id, item_id) on cycle_count_lines.

Upgrade note. Migration 080 does not auto-dedupe. It fails if the database already holds duplicate (count_id, item_id) rows. Find them with:

SELECT count_id, item_id, COUNT(*)
  FROM cycle_count_lines GROUP BY count_id, item_id HAVING COUNT(*) > 1;

Keep one line per pair, delete the surplus and any still-PENDING inventory_adjustments they produced, then apply. A fresh install applies it immediately.

Mobile

The cycle-count screen changes, so the mobile build moves to version 1.33.0, versionCode 12. The APK is rebuilt at the end of the current migration round rather than per release.

Verification

Merged-main suites: api 2881 passed / 9 skipped, admin 101 passed, mobile 55 passed.