chore(ci): add govulncheck, staticcheck, go vet, gofumpt gates

* Add lint/format checks to the Gitea release workflow and Makefile
  (targets: vet, fmt, fmt-check, staticcheck, govulncheck, check)
* Switch .golangci.json formatter from gofmt to gofumpt (extra.group-params)
* Bump golang.org/x/text 0.37.0 -> 0.39.0 for GO-2026-5970; re-vendor
* Fix staticcheck S1011 in pkg/diff; drop unused pgsql writer helpers
* Fix gocritic unnamedResult (pkg/diff) and rangeValCopy (pkg/pgsql)
* Apply gofumpt + goimports formatting across the tree

tests/assets/gorm/complex.go

@@ -49,12 +49,12 @@ func (ModelPost) TableName() string {
 
 // ModelComment represents a comment on a post
 type ModelComment struct {
-	ID        int64      `gorm:"column:id;primaryKey;autoIncrement;type:bigint"`
-	PostID    int64      `gorm:"column:post_id;type:bigint;not null;index:idx_post_id"`
-	UserID    *int64     `gorm:"column:user_id;type:bigint;index:idx_user_id"`
-	Content   string     `gorm:"column:content;type:text;not null"`
-	CreatedAt time.Time  `gorm:"column:created_at;type:timestamp;default:now()"`
-	UpdatedAt time.Time  `gorm:"column:updated_at;type:timestamp;default:now()"`
+	ID        int64     `gorm:"column:id;primaryKey;autoIncrement;type:bigint"`
+	PostID    int64     `gorm:"column:post_id;type:bigint;not null;index:idx_post_id"`
+	UserID    *int64    `gorm:"column:user_id;type:bigint;index:idx_user_id"`
+	Content   string    `gorm:"column:content;type:text;not null"`
+	CreatedAt time.Time `gorm:"column:created_at;type:timestamp;default:now()"`
+	UpdatedAt time.Time `gorm:"column:updated_at;type:timestamp;default:now()"`
 
 	Post *ModelPost `gorm:"foreignKey:PostID;references:ID;constraint:OnDelete:CASCADE"`
 	User *ModelUser `gorm:"foreignKey:UserID;references:ID;constraint:OnDelete:SET NULL"`