feat: Portal, Email Inbound, Discuss + module improvements

- Portal: /my/* routes, signup, password reset, portal user support
- Email Inbound: IMAP polling (go-imap/v2), thread matching
- Discuss: mail.channel, long-polling bus, DM, unread count
- Cron: ir.cron runner (goroutine scheduler)
- Bank Import, CSV/Excel Import
- Automation (ir.actions.server)
- Fetchmail service
- HR Payroll model
- Various fixes across account, sale, stock, purchase, crm, hr, project

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

addons/account/models/account_tax_calc.go

@@ -51,10 +51,12 @@ func ComputeTax(env *orm.Environment, taxID int64, baseAmount float64) (*TaxResu
 	case "fixed":
 		taxAmount = amount
 	case "division":
+		// Division tax: price = base / (1 - rate/100)
+		// Mirrors: odoo/addons/account/models/account_tax.py _compute_amount (division case)
 		if priceInclude {
-			taxAmount = baseAmount - (baseAmount / (1 + amount/100))
+			taxAmount = baseAmount - (baseAmount * (100 - amount) / 100)
 		} else {
-			taxAmount = baseAmount * amount / 100
+			taxAmount = baseAmount/(1-amount/100) - baseAmount
 		}
 	}