Set the chart's placeholder version to 0.20.1

Cosmetic: make helm-package sets the published version and appVersion
from the tag, so these two fields decide nothing (see the comment
above them). Kept in step anyway, same as e77f04b and 429d5fd, so a
tree heading for v0.20.1 doesn't say 0.20.0.

Claude-Session: https://claude.ai/code/session_01RHPj4ggeFdEjKKfm4SHbD7

charts/terdut-server/Chart.yaml

@@ -15,5 +15,5 @@ type: application
 # appVersion and image.tag in values.yaml no longer agree, and that is not an oversight:
 # image.tag stays "latest", which is what a local install actually pulls. appVersion is
 # metadata and drives nothing.
-version: 0.20.0
-appVersion: "v0.20.0"
+version: 0.20.1
+appVersion: "v0.20.1"

internal/db/db.go

@@ -5,6 +5,7 @@ import (
 	"embed"
 	"fmt"
 	"io/fs"
+	"log"
 	"sort"
 	"strings"
 	"time"
@@ -15,6 +16,19 @@ import (
 //go:embed migrations
 var migrationsFS embed.FS
 
+// pingAttempts and pingRetryDelay bound the retry on the first connection.
+// This pod's own IP can reach the Postgres pod's node before that node's
+// NetworkPolicy enforcement (kube-router, reacting to the pod's creation
+// event) has added it to the allowed-source set, which fails the ping with
+// "connection refused" rather than a timeout. That race resolves within
+// several seconds in practice; five attempts two seconds apart give it
+// comfortable room without turning a genuinely absent database into a long
+// hang.
+const (
+	pingAttempts   = 5
+	pingRetryDelay = 2 * time.Second
+)
+
 // Open connects to Postgres. dsn is a libpq connection string or URL, e.g.
 // postgres://terdut:secret@localhost:5432/terdut?sslmode=disable.
 //
@@ -33,11 +47,19 @@ func Open(dsn string) (*sql.DB, error) {
 	db.SetMaxOpenConns(10)
 	db.SetMaxIdleConns(5)
 	db.SetConnMaxLifetime(time.Hour)
-	if err := db.Ping(); err != nil {
+
+	for attempt := 1; ; attempt++ {
+		err = db.Ping()
+		if err == nil {
+			return db, nil
+		}
+		if attempt == pingAttempts {
 			db.Close()
 			return nil, fmt.Errorf("ping: %w", err)
 		}
-	return db, nil
+		log.Printf("open db: ping attempt %d/%d failed, retrying in %s: %v", attempt, pingAttempts, pingRetryDelay, err)
+		time.Sleep(pingRetryDelay)
+	}
 }
 
 // Migrate applies every embedded migration that has not been applied yet, in