refactor: rename Processor to Webhook and Webhook to Entrypoint

The top-level entity that groups entrypoints and targets is now called
Webhook (was Processor). The inbound URL endpoint entity is now called
Entrypoint (was Webhook). This rename affects database models, handler
comments, routes, and README documentation.

closes #12

internal/handlers/webhook.go

@@ -6,19 +6,19 @@ import (
 	"github.com/go-chi/chi"
 )
 
-// HandleWebhook handles incoming webhook requests
+// HandleWebhook handles incoming webhook requests at entrypoint URLs
 func (h *Handlers) HandleWebhook() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		// Get webhook UUID from URL
-		webhookUUID := chi.URLParam(r, "uuid")
-		if webhookUUID == "" {
+		// Get entrypoint UUID from URL
+		entrypointUUID := chi.URLParam(r, "uuid")
+		if entrypointUUID == "" {
 			http.NotFound(w, r)
 			return
 		}
 
 		// Log the incoming webhook request
 		h.log.Info("webhook request received",
-			"uuid", webhookUUID,
+			"entrypoint_uuid", entrypointUUID,
 			"method", r.Method,
 			"remote_addr", r.RemoteAddr,
 			"user_agent", r.UserAgent(),
@@ -32,7 +32,7 @@ func (h *Handlers) HandleWebhook() http.HandlerFunc {
 		}
 
 		// TODO: Implement webhook handling logic
-		// For now, return "unimplemented" for all webhook POST requests
+		// Look up entrypoint by UUID, find parent webhook, fan out to targets
 		w.WriteHeader(http.StatusNotFound)
 		_, err := w.Write([]byte("unimplemented"))
 		if err != nil {