feat: add env vars to disable render endpoints

BLOCKY_DISABLE_GLB/PNG/GIF/MP4 return 403 when set to true

internal/config/config.go

@@ -0,0 +1,31 @@
+package config
+
+import (
+	"os"
+	"strings"
+)
+
+// EndpointConfig holds enable/disable flags for render endpoints
+type EndpointConfig struct {
+	GLBEnabled bool
+	PNGEnabled bool
+	GIFEnabled bool
+	MP4Enabled bool
+}
+
+// LoadEndpointConfig reads endpoint configuration from environment variables.
+// All endpoints are enabled by default.
+// Set BLOCKY_DISABLE_GLB=true, BLOCKY_DISABLE_PNG=true, etc. to disable.
+func LoadEndpointConfig() *EndpointConfig {
+	return &EndpointConfig{
+		GLBEnabled: !isDisabled("BLOCKY_DISABLE_GLB"),
+		PNGEnabled: !isDisabled("BLOCKY_DISABLE_PNG"),
+		GIFEnabled: !isDisabled("BLOCKY_DISABLE_GIF"),
+		MP4Enabled: !isDisabled("BLOCKY_DISABLE_MP4"),
+	}
+}
+
+func isDisabled(envVar string) bool {
+	val := strings.ToLower(os.Getenv(envVar))
+	return val == "true" || val == "1" || val == "yes"
+}