PDF invoice reports + SMTP email sending

PDF Reports:
- Professional invoice HTML renderer (company header, partner address,
  styled line items, totals, Odoo-purple branding, A4 @page CSS)
- wkhtmltopdf installed in Docker runtime stage for real PDF generation
- Print button on invoice form (opens PDF in new tab)
- Exported HtmlToPDF/RenderInvoiceHTML for cross-package use

SMTP Email:
- SendEmail + SendEmailWithAttachments with MIME multipart support
- Base64 file attachments
- Config via ODOO_SMTP_HOST/PORT/USER/PASSWORD/FROM env vars
- LoadSMTPConfig helper, nil auth for relay servers

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/tools/config.go

@@ -37,6 +37,13 @@ type Config struct {
 	// Limits
 	LimitMemorySoft int64
 	LimitTimeReal   int
+
+	// SMTP Email
+	SMTPHost     string
+	SMTPPort     int
+	SMTPUser     string
+	SMTPPassword string
+	SMTPFrom     string
 }
 
 // DefaultConfig returns a configuration with default values.
@@ -54,6 +61,7 @@ func DefaultConfig() *Config {
 		Workers:       0,
 		DataDir:       "/var/lib/odoo",
 		LogLevel:      "info",
+		SMTPPort:      587,
 	}
 }
 
@@ -104,6 +112,23 @@ func (c *Config) LoadFromEnv() {
 	if v := os.Getenv("ODOO_BUILD_DIR"); v != "" {
 		c.BuildDir = v
 	}
+	if v := os.Getenv("ODOO_SMTP_HOST"); v != "" {
+		c.SMTPHost = v
+	}
+	if v := os.Getenv("ODOO_SMTP_PORT"); v != "" {
+		if p, err := strconv.Atoi(v); err == nil {
+			c.SMTPPort = p
+		}
+	}
+	if v := os.Getenv("ODOO_SMTP_USER"); v != "" {
+		c.SMTPUser = v
+	}
+	if v := os.Getenv("ODOO_SMTP_PASSWORD"); v != "" {
+		c.SMTPPassword = v
+	}
+	if v := os.Getenv("ODOO_SMTP_FROM"); v != "" {
+		c.SMTPFrom = v
+	}
 }
 
 // DSN returns the PostgreSQL connection string.