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.

Generated with [Devin](https://devin.ai)

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

CHANGELOG.md

@@ -21,6 +21,8 @@ All notable changes to Primora. Format follows [Keep a Changelog](https://keepac
 - **Telemetry alert rules** (`core.alert_rules`, migration 00012) — `heartbeat_silence` (component quiet for N minutes) and `error_spike` (≥N errors in a sliding window) rules per project, evaluated every 60 s. Rules fire on state transitions only: `alert.fired` once when breached, `alert.resolved` on recovery — both are first-class webhook event types and ride the existing signed dispatcher + realtime stream. API: `GET/POST /projects/:id/alerts`, `PUT/DELETE …/alerts/:ruleID`; dashboard manages them from Integrations → Webhooks; `firing` shows the breached components.
 - **Inbound webhooks** (`core.inbound_hooks`, migration 00013) — public ingest endpoints `POST /api/v1/hooks/<token>` (the token is the credential). `event` mode republishes the body as `inbound.received` domain events through the signed dispatcher + realtime; `job` mode triggers a scheduled-job run with the received body as its payload (`triggered_by: "hook"`). Optional `secret` requires `X-Primora-Signature` HMAC-SHA256 — the same scheme outbound deliveries use. Bodies capped at 256 KiB. Managed from Integrations → Webhooks.
 - **Document filtering and ordering** — `GET /collections/:id/documents` accepts `filter` (comma-separated `field.op.value`; ops `eq neq gt gte lt lte like in is`; dotted paths index into document data, `id`/`created_at`/`updated_at` filterable) and `order` (`field.asc|field.desc` list). Whitelisted parsing + parameterized values; plain lists unchanged. CLI: `primora documents list --collection <slug> --filter … --order …`.
+- **HA scheduler leadership** — the job scheduler and alert evaluator each hold a session-scoped PostgreSQL advisory lock on a dedicated pinned connection, so multiple backend replicas scan for due work exactly once; manual and hook-triggered runs remain available on any replica. Leadership is released on shutdown and fails over automatically when a replica dies — verified live with a two-replica test.
+- **Email templates + send log** (`core.email_log`, migration 00014) — the mailer renders registered templates (currently `invitation`) and every send — successful or failed — is recorded with template, recipient, subject, status, and error text. `GET /projects/:id/emails` lists recent sends; the Members page shows an "Email log" card under pending invitations.
 
 ## [0.7.1] - 2026-09-23