Feat[BE]: create project budget repo, entity, and migration

internal/entities/project_budget.go

@@ -0,0 +1,15 @@
+package entities
+
+import (
+	"time"
+)
+
+type ProjectBudget struct {
+	Id        uint      `gorm:"primaryKey"`
+	Qty       float64   `gorm:"type:numeric(15,3);not null"`
+	Price     float64   `gorm:"type:numeric(15,3);not null"`
+	CreatedAt time.Time `gorm:"autoCreateTime"`
+
+	Nonstock     *Nonstock     `gorm:"foreignKey:Id;references:Id"`
+	ProjectFlock *ProjectFlock `gorm:"foreignKey:Id;references:Id"`
+}