Add a wiring list dialog and an excluded-conductor count

Slice 4 of discussion #503, on top of slice 3 (#629): the smallest
surface that makes wiring_list_view visible, plus the diagnostic the
view needs to be honest about what it is missing.

Projet > "Liste de câblage (base de données)" opens a read-only table of
wiring_list_view, headed by a line stating how many conductors are
listed and, when non-zero, how many were excluded and why.

Deliberately not another exporter. QET already ships a wiring-list CSV
export (Projet > Exporter le plan de câblage, and --export-cables) which
walks the project XML; measured on the same projects it produces a row
per conductor and resolves labels correctly when the project has them.
Adding a second, competing CSV would be worse, not better -- the
database path's value is what it unlocks (terminal plans, BOM joins),
not replacing that export.

projectDataBase::excludedConductorCount() counts, from the live scene,
the conductors deliberately absent from the conductor table because a
terminal has no uuid. Counted from the scene precisely because the
database is where those conductors are not. Verified: 671 on
examples/industrial.qet (which has 1794 terminals and no terminal uuids
at all, so its list is empty and now says so), 0 on a project whose
elements do carry terminal uuids.

KNOWN GAP, not fixed here and the reason this is opened for discussion
rather than merge: after a save/reload the component columns are blank
for slave elements. populateElementTable()/populateElementInfoTable()
only insert Simple|Terminal|Master|Thumbnail, so slave elements -- relay
contacts, i.e. a large share of real wire endpoints -- have no row in
element_info for the view to read a label from. Measured on a two-slave-
contact project after reload: element rows 0, element_info rows 0,
terminal rows 2, conductor rows 1; the wire is listed (slice 3's LEFT
JOIN keeps it) but both component names are empty, where the existing
CSV export shows K1 -> K2 for the same file.

Closing that gap means widening a filter shared with the nomenclature
and summary views, which would change what those existing, shipped
features contain. That is a maintainer decision, not one to take
unilaterally inside an additive slice.

sources/dataBase/projectdatabase.cpp

@@ -111,6 +111,42 @@ QSqlQuery projectDataBase::newQuery(const QString &query) {
 	return QSqlQuery(query, m_data_base);
 }
 
+/**
+	@brief projectDataBase::excludedConductorCount
+	@return how many conductors of the project are deliberately absent from
+	the conductor table because at least one of their terminals has no uuid.
+
+	Counted from the live scene rather than from the database, precisely
+	because the database is where these conductors are *not*. See
+	addConductor() for why they are omitted: a terminal uuid comes from the
+	catalog .elmt definition, so an element whose definition predates that
+	field yields terminals with no stable identity to key on.
+
+	This is what lets a caller tell the user "N wires are missing and here
+	is why", instead of silently presenting a short list as if it were
+	complete.
+*/
+int projectDataBase::excludedConductorCount() const
+{
+	if (!m_project) {
+		return 0;
+	}
+
+	int count = 0;
+	for (auto *diagram : m_project->diagrams())
+	{
+		const auto conductor_list = diagram->conductors();
+		for (auto *conductor : conductor_list)
+		{
+			if (conductor->terminal1->uuid().isNull()
+				|| conductor->terminal2->uuid().isNull()) {
+				++count;
+			}
+		}
+	}
+	return count;
+}
+
 /**
 	@brief projectDataBase::addElement
 	@param element