Add documentation for most sold stock items query

Care/Operations/mostsold_ssmm.md

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+
+# Most Sold Stock Items
+
+> Total quantity dispensed, selling price, purchase price, and margin per stock item
+
+## Purpose
+
+Identifies the most-selling stock items by aggregating dispensed quantities and computing the gross margin (selling price minus purchase cost).
+
+## Parameters
+
+| Parameter | Type | Description | Example |
+|-----------|------|-------------|---------|
+| `stock_name` | TEXT | Filter by stock item name (exact match) | `'Paracetamol'` |
+| `DATE` | DATE | Filter by date range on the charge item | `2026-05-01` |
+
+---
+
+## Query
+
+```sql
+SELECT 
+    pk.name AS stock_name,
+    SUM(md.quantity) AS total_quantity_dispensed,
+    SUM(ci.total_price) AS selling_price,
+    SUM(p.purchase_price * md.quantity) AS purchase_price,
+    SUM(ci.total_price - (p.purchase_price * md.quantity)) AS total_margin  
+FROM emr_medicationdispense md
+JOIN emr_chargeitem ci ON md.charge_item_id = ci.id         
+JOIN emr_chargeitemdefinition cid ON ci.charge_item_definition_id = cid.id 
+JOIN emr_product p ON p.charge_item_definition_id = cid.id
+JOIN emr_productknowledge pk ON p.product_knowledge_id = pk.id
+WHERE md.status IN ('completed', 'in_progress', 'preparation')  
+  AND md.deleted = FALSE                                         
+  AND ci.status IN ('billed', 'paid')
+  --[[AND pk.name = {{stock_name}}]]
+  --[[AND {{DATE}}]]  
+GROUP BY pk.name
+ORDER BY total_quantity_dispensed DESC;
+```
+
+
+## Notes
+
+- Only non-deleted medication dispenses are included.
+- Dispense status is filtered to `completed`, `in_progress`, and `preparation` to capture both fulfilled and active dispenses.
+- Charge item status is filtered to `billed` and `paid` to ensure only items that have generated revenue are counted.
+- Metabase-specific filters (`[[...]]`) allow dynamic filtering in dashboards.
+- Results are ordered by highest dispensed quantity first.
+
+*Last updated: 2026-05-12*
+
+