Make English the source language of the interface text

Every tr() source string in the code and the forms is now the English
text, and French is a translation (qet_fr.ts) like the other languages.
Generated, not hand-edited: master ef795a21e5 converted by
qet-en-source (harness 4c4ddc9).

3144 messages get an English source, 665 already had one, 0 left French; 8 shared-wording pairs disambiguated.
C++: 2904 literals in 233 files. Forms: 809 strings in 65 files. All 34 .ts files re-keyed; qet_fr.ts filled.
lupdate check: PASS. What each of 38 languages shows, old vs new: same 118266, English instead of French 38433, comment fallback 51, differences 0.

sources/autoNum/ui/pastenumberingimport.cpp

@@ -62,10 +62,11 @@ void PasteNumberingImport::push(QWidget *parent,
 	}
 	const auto answer = QET::QetMessageBox::question(
 				parent,
-				tr("Numérotation absente de ce projet"),
-				tr("Les éléments collés suivent %n numérotation(s) qui n'existe(nt) pas dans ce projet : %1.\n\n"
-				   "Les importer ? Les éléments recevront alors les prochains numéros, à partir de 1. "
-				   "Sinon ils seront collés sans numérotation.", "", static_cast<int>(missing.size()))
+				tr("Numbering missing from this project"),
+				tr("The pasted elements follow %n numberings that do not exist in this project: %1.\n"
+				   "\n"
+				   "Import them? The elements will then receive the next numbers, starting from 1. Otherwise "
+				   "they will be pasted without numbering.", "", static_cast<int>(missing.size()))
 				.arg(names.join(QStringLiteral(", "))),
 				QMessageBox::Yes | QMessageBox::No,
 				QMessageBox::Yes);