Spell out the Shift-drag hint on symbol texts

Hovering a symbol's text shows its value and the hint "<Shift> to move"
("<Shift> pour déplacer" in French), which does not say what moves: a
plain drag moves the whole symbol, Shift+drag moves the text alone
(DynamicElementTextItem::mousePressEvent).

English: "Hold Shift and drag to move this text on its own".
French: "Maintenir Maj et faire glisser pour déplacer ce texte seul".

Translations only, as for #1124: the source string is unchanged, so the
other languages keep their current text.

Revives #499 (closed 2026-06-11 by its author to test locally first).

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

lang/qet_en.ts

@@ -1936,7 +1936,7 @@ Note: these options DO NOT allow or block auto numberings, only their update pol
         <source>
 &lt;Shift&gt; to move</source>
         <translation>
-&lt;Shift&gt; to move</translation>
+Hold Shift and drag to move this text on its own</translation>
     </message>
 </context>
 <context>

lang/qet_fr.ts

@@ -1935,7 +1935,7 @@ Remarque: Ces options n'autorisent ou bloquent l'auto numérotation, s
         <source>
 &lt;Shift&gt; to move</source>
         <translation>
-&lt;Shift&gt; pour déplacer</translation>
+Maintenir Maj et faire glisser pour déplacer ce texte seul</translation>
     </message>
 </context>
 <context>