fix(api-token): hash tokens at rest and show plaintext only once

Store API tokens as SHA-256 hashes instead of plaintext and return the token value only in the create response. List no longer exposes the token, and the UI drops the Show/Copy buttons in favor of a one-time reveal modal at creation.

Match hashes the presented bearer token before the constant-time compare, and a migration hashes any pre-existing plaintext rows in place so existing tokens keep authenticating. Docs and translations updated.

database/model/model.go

@@ -138,7 +138,7 @@ type HistoryOfSeeders struct {
 type ApiToken struct {
 	Id        int    `json:"id" gorm:"primaryKey;autoIncrement"`
 	Name      string `json:"name" gorm:"uniqueIndex;not null"`
-	Token     string `json:"token" gorm:"not null"`
+	Token     string `json:"token" gorm:"not null"` // SHA-256 hash; the plaintext is shown only once at creation
 	Enabled   bool   `json:"enabled" gorm:"default:true"`
 	CreatedAt int64  `json:"createdAt" gorm:"autoCreateTime:milli"`
 }