Add "prefer SMTP" toggle to skip Microsoft Graph for email

When the M365 connector is connected the app always tries Graph first,
and a Graph 202 ends the send — so report mail to recipients Exchange
silently drops (Google-hosted subdomains of the O365 domain) never
reaches them, even with working SMTP configured.

New prefer_smtp flag gates all three Graph branches (smtp_test,
send_report, _maybe_send_auto_email) so they go straight to SMTP. UI
toggle #st-smtpPreferSmtp in Settings → E-mailrapport, saved/loaded by
scheduler.js, with da/de/en strings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

templates/index.html

@@ -845,6 +845,10 @@ document.addEventListener('DOMContentLoaded', applyI18n);
             <label data-i18n="m365_smtp_auto_email_manual">Email report after manual scan</label>
             <label class="toggle" style="flex:unset"><input type="checkbox" id="st-smtpAutoEmail"><span class="toggle-slider"></span></label>
           </div>
+          <div class="settings-row">
+            <label data-i18n="m365_smtp_prefer_smtp">Always send via SMTP (skip Microsoft Graph)</label>
+            <label class="toggle" style="flex:unset"><input type="checkbox" id="st-smtpPreferSmtp"><span class="toggle-slider"></span></label>
+          </div>
           <div style="display:flex;justify-content:flex-end;gap:8px;margin-top:4px">
             <div id="st-smtpStatus" style="flex:1;font-size:11px;color:var(--muted);align-self:center"></div>
             <button onclick="stSmtpSave()" style="background:none;border:1px solid var(--border);color:var(--muted);height:26px;padding:0 12px;border-radius:6px;font-size:12px;cursor:pointer;box-sizing:border-box" data-i18n="btn_save">Save</button>