feat(05-01): restructure fonoteka plugins into Winter directories

- Move models, classes, controllers, middleware, and updates into subpackages
- Add self-registering models/updates/classes registries so later plans add files
- Keep the genres route and shipped migration SQL unchanged

models/user.go

@@ -0,0 +1,15 @@
+package models
+
+// User is the minimal users row the JWT guard loads.
+type User struct {
+	ID                 uint   `gorm:"column:id;primaryKey"`
+	Email              string `gorm:"column:email"`
+	Password           string `gorm:"column:password"`
+	MustChangePassword bool   `gorm:"column:must_change_password"`
+}
+
+func (User) TableName() string { return "users" }
+
+func init() {
+	Register(User{})
+}