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/database/model_target.go

@@ -10,14 +10,14 @@ const (
 	TargetTypeLog      TargetType = "log"
 )
 
-// Target represents a delivery target for a processor
+// Target represents a delivery target for a webhook
 type Target struct {
 	BaseModel
 
-	ProcessorID string     `gorm:"type:uuid;not null" json:"processor_id"`
-	Name        string     `gorm:"not null" json:"name"`
-	Type        TargetType `gorm:"not null" json:"type"`
-	Active      bool       `gorm:"default:true" json:"active"`
+	WebhookID string     `gorm:"type:uuid;not null" json:"webhook_id"`
+	Name      string     `gorm:"not null" json:"name"`
+	Type      TargetType `gorm:"not null" json:"type"`
+	Active    bool       `gorm:"default:true" json:"active"`
 
 	// Configuration fields (JSON stored based on type)
 	Config string `gorm:"type:text" json:"config"` // JSON configuration
@@ -27,6 +27,6 @@ type Target struct {
 	MaxQueueSize int `json:"max_queue_size,omitempty"`
 
 	// Relations
-	Processor  Processor  `json:"processor,omitempty"`
+	Webhook    Webhook    `json:"webhook,omitempty"`
 	Deliveries []Delivery `json:"deliveries,omitempty"`
 }