fix: dedupe and report automatic template creation from images

install_appliances_from_image relied on the name+version pair check in
TemplatesService, so the same appliance reached through a second image
(the CSR1000v case) created a second template sharing the name. The auto
path now skips when any template with the same name exists, whatever the
version, and returns a manifest of created and skipped candidates;
POST /images/install replies 200 with that manifest instead of an empty
204, and the image_install MCP tool surfaces it.

gns3server/db/repositories/templates.py

@@ -71,6 +71,17 @@ class TemplatesRepository(BaseRepository):
         result = await self._db_session.execute(query)
         return result.scalars().first()
 
+    async def get_template_by_name(self, name: str) -> Union[None, models.Template]:
+        """
+        Return the first template with this name, regardless of version.
+        """
+
+        query = select(models.Template).\
+            options(selectinload(models.Template.images)).\
+            where(models.Template.name == name)
+        result = await self._db_session.execute(query)
+        return result.scalars().first()
+
     async def get_templates(self) -> List[models.Template]:
 
         query = select(models.Template).options(selectinload(models.Template.images))