Add %T, the target folio's title, to report and cross reference formulas

A folio report could name the folio it points to by position (%f), folio
number (%F), installation (%M) and location (%LM), but not by its title.
EPLAN and other tools print references like "+UV1/1 Versorgung UG/EG.0",
which with %T is the formula "+%LM/%F %T.%c".

- FormulaContext carries the folio title, filled from the title block.
- %T is replaced on its own only, not as the start of a longer word.
- A report whose formula uses %T follows the target folio's title block
  (BorderTitleBlock::informationChanged), as %F already follows its
  folio number.
- The report and cross reference property pages list %T.

tst_reportfoliotitle checks the replacement, that %total and title
block variables keep their values, and an empty title.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

sources/ui/reportpropertiewidget.ui

@@ -38,6 +38,7 @@ Create your own text using the following variables:
 %F: the sheet number
 %M: the installation
 %LM: the location
+%T: the sheet title
 %l: the row number
 %c: the column number</string>
           </property>

sources/ui/xrefpropertieswidget.ui

@@ -285,7 +285,8 @@
 %l: the row number
 %c: the column number
 %M: the installation
-%LM: the location</string>
+%LM: the location
+%T: the sheet title</string>
           </property>
          </widget>
         </item>