i18n: Translate all Chinese to English across the codebase

Translate Chinese comments, log/error messages, validator labels and
Swagger annotations to English throughout the source code, generated
Swagger docs, config files and CI workflows.

Make the English README primary: README.md now holds the English docs
and README_EN.md holds the Chinese version, with cross-language links
updated accordingly.

Note: the generated docs/ swagger files were translated in place; run
`go generate ./...` (swag init) to regenerate them from the now-English
annotations when a Go toolchain is available.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

model/tag.go

@@ -4,7 +4,7 @@ type Tag struct {
 	IdModel
 	Name         string                 `json:"name" gorm:"default:'';not null;"`
 	UserId       uint                   `json:"user_id" gorm:"default:0;not null;index"`
-	Color        uint                   `json:"color" gorm:"default:0;not null;"` //color 是flutter的颜色值,从0x00000000 到 0xFFFFFFFF; 前两位表示透明度，后面6位表示颜色, 可以转成rgba
+	Color        uint                   `json:"color" gorm:"default:0;not null;"` //color is a flutter color value, from 0x00000000 to 0xFFFFFFFF; the first two digits represent the alpha (transparency), the remaining 6 digits represent the color, can be converted to rgba
 	CollectionId uint                   `json:"collection_id" gorm:"default:0;not null;index"`
 	Collection   *AddressBookCollection `json:"collection,omitempty"`
 	TimeModel