fix(api): avoid NRE in MailSender on rdv query notifications

The API did not bind the Smtp section and its appsettings lacked
Site.Owner, so MailSender threw a NullReferenceException and
PostQuery returned 500. Bind Smtp in the API, add Owner/Smtp to the
api appsettings template, and log/skip sending when mail
configuration is incomplete.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Changelog
 
+## [1.0.8-rc30] - unstable
+
+### Added
+
+### Changed
+
+### Fixed
+
 ## [1.0.8-rc29] - unstable
 
 ### Added
@@ -19,6 +27,14 @@
 
 * [PostIt] Mise a jour d'Avalonia vers 12.1.4.
 
+### Fixed
+
+* [Yavsc.Api, Yavsc.Server] Une demande de rendez-vous ne provoque plus
+  d'erreur 500 (NullReferenceException dans MailSender) : l'API lie
+  desormais la section Smtp, le modele appsettings-api fournit Site.Owner
+  et Smtp, et un envoi sans configuration mail complete est journalise
+  puis ignore.
+
 
 ## [1.0.8-rc28] - unstable