Procurement App
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**Purpose**: Manage material catalog, inventory, stock allocation, and local procurement when stock is unavailable.

Responsibilities
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- Maintain material catalog (chargers, cables, mounting hardware, electrical components)
- Track stock levels per zone
- Check material availability for installations
- Allocate materials from zone stock to specific installations
- Create local procurement requests when stock is insufficient
- Manage vendor directory
- Coordinate with Finance for vendor payments

Dependencies
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- **installations** — MaterialAllocation and ProcurementRequest are linked to installations
- **finance** — Vendor payment triggered after local procurement
- **accounts** — Procurement staff, zone-based stock locations

Key Models
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- **Material** — Catalog item with SKU, category, and unit of measurement.
- **MaterialStock** — Inventory levels per material per zone. Includes reorder thresholds.
- **MaterialAllocation** — Records material allocated to a specific installation. Tracks dispatch and delivery status.
- **ProcurementRequest** — Request to procure materials locally when zone stock is insufficient. Tracks cost estimates and vendor assignment.
- **Vendor** — Local vendors for material procurement. Stores payment details (UPI ID, bank account).

Business Rules
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- Stock is zone-scoped — an installation in Zone A can only use stock from Zone A.
- When stock falls below ``reorder_level``, an alert should be generated (future: auto-procurement request).
- Local procurement requires a vendor to be assigned before proceeding.
- Estimated cost must be provided before procurement is approved.
- After materials are received, actual cost is recorded for Finance to process payment.
- Materials can be returned to stock if an installation is cancelled (via ``returned`` allocation status).