terminaldata: add No, Nc, Common types for SW contacts

Extend TerminalData::Type enum with three new semantic values:
- No     : Normally Open terminal of a switch (SW) contact
- Nc     : Normally Closed terminal of a switch (SW) contact
- Common : Common terminal of a switch (SW) contact

Update typeToString() and typeFromString() accordingly.
Fully backward compatible: existing Generic/Inner/Outer types
are unchanged. Elements without typed terminals fall back
to the previous behavior (first 2 named terminals).

terminal: expose terminalType() as public accessor

Add Terminal::terminalType() returning the TerminalData::Type
of this terminal. This allows crossrefitem and other consumers
to filter terminals by semantic role (No, Nc, Common) without
accessing TerminalData internals directly.

terminaleditor: add No, Nc, Common entries to type combobox

Expose the three new TerminalData types (No, Nc, Common) in
the element editor UI so users can assign a semantic role to
each terminal of a SW contact element.

Also fix a pre-existing bug in updateForm() where m_type_cb
was incorrectly using m_orientation_cb->findData() instead
of m_type_cb->findData(), preventing the type from being
restored correctly when selecting a terminal.

terminaleditor: add No, Nc, Common entries to type combobox

Expose the three new TerminalData types (No, Nc, Common) in
the element editor UI so users can assign a semantic role to
each terminal of a SW contact element.

Also fix a pre-existing bug in updateForm() where m_type_cb
was incorrectly using m_orientation_cb->findData() instead
of m_type_cb->findData(), preventing the type from being
restored correctly when selecting a terminal.

sources/properties/terminaldata.h

@@ -41,7 +41,10 @@ class TerminalData : public PropertiesInterface
 		enum Type {
 			Generic,
 			Inner,
-			Outer
+			Outer,
+			No,     ///< Normally Open terminal (for SW contacts)
+			Nc,     ///< Normally Closed terminal (for SW contacts)
+			Common  ///< Common terminal (for SW contacts)
 		};
 		Q_ENUM(Type)