perf: incremental render scale, SQL pagination and observability

- BIRD filter chunking (500 CIDR); bounded job worker pool
- ListModulesPage SQL push-down; revision diff limit; batch revision prune
- DB pool tuning; Prometheus pipeline/job metrics
- Coalesce module_refresh via idempotency; GET /jobs/{id}/report
- JobAuditWriter foundation for job_audit persistence

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/store/memory.go

@@ -382,6 +382,11 @@ func (m *Memory) ListModules(tenantID string) []*Module {
 	return out
 }
 
+func (m *Memory) ListModulesPage(tenantID, cursor string, limit int) ([]*Module, string, bool) {
+	all := m.ListModules(tenantID)
+	return PaginateOffset(all, cursor, limit)
+}
+
 // ListPeers returns BGP peers for a tenant (sorted by name).
 func (m *Memory) ListPeers(tenantID string) []*BGPPeer {
 	m.mu.RLock()