Add purchase report documentation for Pallium

Care/Operations/purchase_report_pallium.md

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+# Purchase Report - Pallium
+
+> Detailed line-level purchase / supply delivery report with supplier, destination, batch, expiry and purchase value
+
+## Purpose
+
+Line-by-line view of stock received via supply deliveries at Pallium. Each row represents one supply delivery and shows the supplier, destination location, product, batch / expiry details, unit purchase price, quantity delivered and the total purchase value.
+
+## Parameters
+
+| Parameter | Type | Description | Example |
+|-----------|------|-------------|---------|
+| `date` | DATE / range | Metabase date filter (typically bound to `sd.created_date`) | `'2026-05-01'` |
+| `supplier_name` | TEXT | Filter by supplier organisation name (exact match) | `'ABC Pharma'` |
+| `stock_name` | TEXT | Filter by product / stock name (exact match) | `'Paracetamol'` |
+
+---
+
+## Query
+
+```sql
+SELECT
+  sd.created_date AS supply_date,
+  org.name AS supplier_name,
+  fl.name AS destination,
+  p.batch->>'lot_number' AS lot_number,
+  p.expiration_date,
+  pk.name AS product_name,
+  p.purchase_price,
+  sd.supplied_item_quantity * p.purchase_price AS total_purchase,
+  sd.supplied_item_quantity AS quantity_delivered
+FROM emr_supplydelivery sd
+JOIN emr_inventoryitem ii ON sd.supplied_inventory_item_id = ii.id
+JOIN emr_product p ON ii.product_id = p.id
+JOIN emr_productknowledge pk ON p.product_knowledge_id = pk.id
+JOIN emr_deliveryorder d ON sd.order_id = d.id
+JOIN emr_organization org ON d.supplier_id = org.id
+JOIN emr_facilitylocation fl ON d.destination_id = fl.id
+WHERE sd.status NOT IN ('entered_in_error', 'abandoned')
+  --[[AND {{date}}]]
+  --[[AND org.name = {{supplier_name}}]]
+  --[[AND pk.name = {{stock_name}}]]
+ORDER BY supplier_name;
+```
+
+## Notes
+
+- **Metabase filters:**
+  - `[[AND {{date}}]]` is a field filter — bind it to `sd.created_date` (or whatever date column you want filterable) in the Metabase variable settings.
+  - `[[AND org.name = {{supplier_name}}]]` and `[[AND pk.name = {{stock_name}}]]` are exact-match text filters on supplier and product name.
+
+*Last updated: 2026-05-25*
+
+````
+