Reduce usage of db.DefaultContext (#27073)

Part of #27065

This reduces the usage of `db.DefaultContext`. I think I've got enough
files for the first PR. When this is merged, I will continue working on
this.

Considering how many files this PR affect, I hope it won't take to long
to merge, so I don't end up in the merge conflict hell.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/auth/linkaccount.go

@@ -142,7 +142,7 @@ func LinkAccountPostSignIn(ctx *context.Context) {
 		return
 	}
 
-	u, _, err := auth_service.UserSignIn(signInForm.UserName, signInForm.Password)
+	u, _, err := auth_service.UserSignIn(ctx, signInForm.UserName, signInForm.Password)
 	if err != nil {
 		handleSignInError(ctx, signInForm.UserName, &signInForm, tplLinkAccount, "UserLinkAccount", err)
 		return