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 <[email protected]>

internal/db/open.go

@@ -6,9 +6,12 @@ import (
 	"errors"
 	"fmt"
 	"io/fs"
+	"os"
 	"path"
 	"sort"
+	"strconv"
 	"strings"
+	"time"
 
 	"evobgp/migrations"
 
@@ -22,6 +25,17 @@ func OpenPostgresPool(ctx context.Context, dsn string) (*pgxpool.Pool, error) {
 	if err != nil {
 		return nil, err
 	}
+	if max := os.Getenv("EVOBGP_DB_MAX_CONNS"); max != "" {
+		if n, err := strconv.Atoi(strings.TrimSpace(max)); err == nil && n > 0 {
+			cfg.MaxConns = int32(n)
+		}
+	}
+	if min := os.Getenv("EVOBGP_DB_MIN_CONNS"); min != "" {
+		if n, err := strconv.Atoi(strings.TrimSpace(min)); err == nil && n >= 0 {
+			cfg.MinConns = int32(n)
+		}
+	}
+	cfg.MaxConnLifetime = 30 * time.Minute
 	pool, err := pgxpool.NewWithConfig(ctx, cfg)
 	if err != nil {
 		return nil, err