notification: payload + Channel interface

internal/notification/channel.go

@@ -0,0 +1,20 @@
+package notification
+
+import (
+	"context"
+	"time"
+)
+
+// Channel is the per-kind transport. Implementations live in
+// webhook.go / ntfy.go / smtp.go. Send must respect ctx (5s for HTTP,
+// 10s for SMTP) and never panic.
+type Channel interface {
+	// Kind returns the kind string ("webhook", "ntfy", "smtp"). Used
+	// for log enrichment and dispatcher routing.
+	Kind() string
+
+	// Send delivers one payload. Returns (statusCode, latency, err).
+	// statusCode is HTTP for HTTP channels, the SMTP final-line code
+	// (e.g. 250) for SMTP, 0 if the call didn't reach a wire response.
+	Send(ctx context.Context, p Payload) (statusCode int, latency time.Duration, err error)
+}