fix: persist docker sqlite settings path

config/config.go

@@ -3,6 +3,8 @@ package config
 import (
 	"crypto/rand"
 	"encoding/base64"
+	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/caarlos0/env/v11"
@@ -30,6 +32,7 @@ func Load() error {
 	if err := env.Parse(&Cfg); err != nil {
 		return err
 	}
+	normalizeDockerSQLiteDSN("/app/data")
 	if strings.TrimSpace(Cfg.JWTSecret) == "" || Cfg.JWTSecret == "infinite-canvas" {
 		secret, err := randomSecret()
 		if err != nil {
@@ -40,6 +43,33 @@ func Load() error {
 	return nil
 }
 
+func normalizeDockerSQLiteDSN(appDataDir string) {
+	driver := strings.ToLower(strings.TrimSpace(Cfg.StorageDriver))
+	if driver != "" && driver != "sqlite" {
+		return
+	}
+	dsn := strings.TrimSpace(Cfg.DatabaseDSN)
+	if dsn == "" || dsn == ":memory:" || strings.HasPrefix(dsn, "file:") {
+		return
+	}
+	pathPart, suffix := dsn, ""
+	if index := strings.Index(dsn, "?"); index >= 0 {
+		pathPart = dsn[:index]
+		suffix = dsn[index:]
+	}
+	if filepath.IsAbs(pathPart) {
+		return
+	}
+	slashPath := filepath.ToSlash(pathPart)
+	if slashPath != "data" && !strings.HasPrefix(slashPath, "data/") {
+		return
+	}
+	if _, err := os.Stat(appDataDir); err != nil {
+		return
+	}
+	Cfg.DatabaseDSN = filepath.Join(filepath.Dir(appDataDir), filepath.FromSlash(slashPath)) + suffix
+}
+
 func randomSecret() (string, error) {
 	buf := make([]byte, 32)
 	if _, err := rand.Read(buf); err != nil {

config/config_test.go

@@ -0,0 +1,33 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestNormalizeDockerSQLiteDSNUsesMountedDataDir(t *testing.T) {
+	root := t.TempDir()
+	appDataDir := filepath.Join(root, "data")
+	if err := os.MkdirAll(appDataDir, 0755); err != nil {
+		t.Fatal(err)
+	}
+	Cfg = Config{StorageDriver: "sqlite", DatabaseDSN: "data/infinite-canvas.db?_pragma=busy_timeout(5000)"}
+
+	normalizeDockerSQLiteDSN(appDataDir)
+
+	want := filepath.Join(root, "data", "infinite-canvas.db") + "?_pragma=busy_timeout(5000)"
+	if Cfg.DatabaseDSN != want {
+		t.Fatalf("DatabaseDSN = %q, want %q", Cfg.DatabaseDSN, want)
+	}
+}
+
+func TestNormalizeDockerSQLiteDSNLeavesLocalPathWithoutMountedDataDir(t *testing.T) {
+	Cfg = Config{StorageDriver: "sqlite", DatabaseDSN: "data/infinite-canvas.db"}
+
+	normalizeDockerSQLiteDSN(filepath.Join(t.TempDir(), "missing-data"))
+
+	if Cfg.DatabaseDSN != "data/infinite-canvas.db" {
+		t.Fatalf("DatabaseDSN = %q, want relative local path", Cfg.DatabaseDSN)
+	}
+}