feat: BOM-aware close-short with inventory reversal transactions

[Blb3D]

Problem

When closing a sales order short on an assembly product, the current close-short logic (#495) adjusts each line independently based on PO quantity_completed. But for assemblies, BOM ratios determine the actual bottleneck:

Real-world example (SO-2026-0044):

• SO for 5 assemblies, each requiring 1 gearbox + 2 keycaps + 3 phone stands
• Production completed: 5 gearboxes, 10 keycaps, 12 phone stands (short by 3)
• Bottleneck: 12 phone stands / 3 per assembly = 4 complete assemblies
• Close short should adjust to: 4 gearboxes, 8 keycaps, 12 phone stands
• Excess goes back to inventory: 1 gearbox + 2 keycaps need receipt transactions back to FG stock
• GL entries: DR Finished Goods (1220), CR WIP (1210) for the excess

Requirements

BOM-aware bottleneck calculation

• Explode the BOM for the order's product
• For each component, calculate produced / bom_ratio = max possible assemblies
• Bottleneck = min() across all components
• Adjust all line quantities proportionally based on bottleneck

Inventory reversal transactions

• For excess produced components (produced > needed after adjustment):
  • Create receipt transaction back to FG inventory
  • GL entry: DR Finished Goods (1220), CR WIP (1210)
• Use TransactionService._create_inventory_transaction() and _create_journal_entry() for atomicity

PO status reconciliation

• Short POs should be closeable independently or as part of SO close-short
• PO detail view needs "Accept Short" / "Close Short" action

Must also handle

• Single-line (non-assembly) orders — simple case, already working in feat: SO line editing and close-short foundation #495
• Multi-line orders with independent products (no shared BOM) — already working
• Multi-level BOMs (sub-assemblies with their own BOMs)
• Orders where some lines are fully complete and only one is short

Depends on

• feat: SO line editing and close-short foundation #495 (foundation: line editing, close-short API, migration, UI)

Files likely touched

• backend/app/services/sales_order_service.py — BOM-aware close_short logic
• backend/app/services/transaction_service.py — inventory reversal + GL entries
• backend/app/services/inventory_service.py — FG receipt back to stock
• backend/app/models/production_order.py — PO close-short status
• frontend/src/pages/admin/OrderDetail.jsx — enhanced close-short modal with BOM breakdown

[coderabbitai]

🔗 Related PRs

#108 - fix: Resolve MRP double-counting of SO and PO demand [merged]
#185 - perf: fix N+1 queries in dashboard and BOM endpoints [merged]
#191 - refactor(frontend): split AdminBOM.jsx god file (ARCHITECT-002) [merged]
#236 - fix: resolve 3 accounting/BOM bugs (#209, #211, #212) [merged]
#462 - fix: allow routing-only items in sales orders [merged]

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