Fix numeric field validation gaps found in review

Address feedback on the width/height/depth elementInformation fields:

- The regex accepted "." alone as a complete value ([0-9]* permits
  zero digits on both sides), meaning a field could be committed with
  a literal "." saved to the XML. Require at least one digit either
  before or after the separator.
- The same pattern was duplicated verbatim in elementinfopartwidget.cpp
  and elementpropertieseditorwidget.cpp's EditorDelegate. Factored into
  QETInformation::numericInfoPattern(), a single shared definition both
  call sites now use.
- Tightened the pattern to at most 2 decimal places (down from 4) to
  match the precision actually meaningful for these fields.

Not changed, by design:
- Storage stays a plain string, consistent with every other numeric
  elementInformation field (quantity etc.) in this codebase -- values
  round-trip through XML text regardless, so a long/micron
  representation wouldn't avoid the string<->number conversion, only
  relocate it.
- No decimal-comma normalization needed: with the fixed pattern, only
  digits and "." are ever accepted at the keystroke level, so an
  alternate separator can't enter the field in the first place.

sources/editor/ui/elementpropertieseditorwidget.cpp

@@ -70,7 +70,7 @@ class EditorDelegate : public QItemDelegate
 			{
 				auto *line_edit = new QLineEdit(parent);
 				auto *validator = new QRegularExpressionValidator(
-					QRegularExpression(QStringLiteral(R"(^[0-9]*\.?[0-9]{0,4}$)")), line_edit);
+					QETInformation::numericInfoPattern(), line_edit);
 				line_edit->setValidator(validator);
 				line_edit->setPlaceholderText(tr("ex. 80.5"));
 				line_edit->setToolTip(tr("Nombre décimal avec un point comme séparateur (ex. 80.5)"));