fix(migrations): make runner robust for all tenant DBs

- Register all missing migrations in runner.py
- Make v4.3 idempotent (rename xml_unsigned only if exists)
- Make v3.3 idempotent (skip warehouse_inventory/purchase_order_items ops when tables/columns missing)
- Mark v3.3.1 and v3.9 as master-only (SKIP)
- Mark v3.5.1 as optional (skip if whatsapp tables missing)
- Runner skips files marked with '-- : SKIP'

pos/migrations/v3.9_supplier_catalog_prices.sql

@@ -1,6 +1,8 @@
+-- : SKIP
 -- v3.9_supplier_catalog_prices.sql
 -- Per-tenant supplier pricing for items in the master supplier_catalog.
 -- This table lives in the master DB and is joined by tenant_id.
+-- Apply manually to the master database.
 
 CREATE TABLE IF NOT EXISTS supplier_catalog_prices (
     id              SERIAL PRIMARY KEY,