Fix AppStream metadata

Reported by appstream validate-tree:

    leocad.appdata.xml
      I: org.leocad.LeoCAD:15: developer-name-tag-deprecated
         The toplevel `developer_name` element is deprecated. Please use the `name` element in a
         `developer` block instead.

      I: org.leocad.LeoCAD:~: developer-info-missing
         This component contains no `developer` element with information about its author.

      W: org.leocad.LeoCAD:~: metainfo-filename-cid-mismatch
         The metainfo filename does not match the component ID.

    ✘ Validation failed: warnings: 1, infos: 2, pedantic: 2

leocad.pro

@@ -138,7 +138,7 @@ unix:!macx {
 	mime.path = $$MIME_DIR
 	mime.files = qt/leocad.xml
 	appdata.path = $$APPDATA_DIR
-	appdata.files = tools/setup/leocad.appdata.xml
+	appdata.files = tools/setup/org.leocad.LeoCAD.appdata.xml
 
 	INSTALLS += target docs man desktop icons mime appdata
 

snapcraft.yaml

@@ -32,7 +32,7 @@ parts:
       - libqt5printsupport5
       - libqt5xml5
     source: https://github.com/leozide/leocad/archive/v26.09.tar.gz
-    parse-info: [usr/share/metainfo/leocad.appdata.xml]
+    parse-info: [usr/share/metainfo/org.leocad.LeoCAD.appdata.xml]
   library:
     source: .
     plugin: dump

tools/setup/org.leocad.LeoCAD.appdata.xml

@@ -12,7 +12,7 @@
 	<launchable type="desktop-id">leocad.desktop</launchable>
 	<url type="homepage">https://www.leocad.org/</url>
 	<url type="bugtracker">https://github.com/leozide/leocad/issues</url>
-  <developer_name>LeoCAD.org</developer_name>
+	<developer id="org.leocad"><name>LeoCAD.org</name></developer>
 	<screenshots>
 		<screenshot type="default">
 			<image>https://www.leocad.org/towerbridge.png</image>