feat: HA scheduler leadership + templated email log

HA scheduler: the job scheduler and alert evaluator hold session-scoped
PostgreSQL advisory locks on pinned pool connections — replicas scan for
due work exactly once, failover verified live with two replicas. Manual
and hook-triggered runs stay available on any replica.

Email surface: mailer renders registered templates (invitation); every
send is logged to core.email_log with status and error text. New
GET /projects/:id/emails endpoint; Members page shows an Email log card.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/frontend/src/App.tsx

@@ -1722,6 +1722,8 @@ export default function App() {
 
           <Show when={activeView() === "members"}>
             <MembersPage
+              projectID={activeProject()?.id}
+              demoMode={isDemo}
               organizationMembers={organizationMembers()}
               organizationInvitations={organizationInvitations()}
               projectMembers={projectMembers()}