feat(api): CRUD files/folders + upload multipart réels (scope owner, soft-delete, conteurs d'erreurs)

- repository.Resources (insert/list/get/soft-delete scoping owner_id, UNIQUE(parent_id,name) → NAME_CONFLICT) + Devices.Upsert au register
- service.Resources : DTOs {id,name,size,mimeType,folderId,createdAt,updatedAt}, upload → UPLOAD_DIR/<device>/<id>.<ext> (nettoyage si métadonnée échoue)
- handlers : files list/get/delete/upload + folders racines ; routes consolidées dans handlers.RegisterRoutes
- dbtest package : test DB jetée par repo (open+reset+migrate, skip si PG down) ; tests repository + handlers end-to-end (register→token→CRUD, scoping cross-device, FILE_TOO_LARGE, NAME_CONFLICT)
- docs: /devices persiste le device, layout UPLOAD_DIR par device, codes NAME_CONFLICT/SERVICE_UNAVAILABLE

backend/dbtest/dbtest.go

@@ -0,0 +1,97 @@
+package dbtest
+
+import (
+	"database/sql"
+	"fmt"
+	"net/url"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/lib/pq"
+
+	"github.com/vaultdrop/backend/db"
+)
+
+// OpenTestDatabase ensures the test database exists, resets its schema, runs
+// all migrations, and returns a live connection (closed via t.Cleanup).
+// Tests are skipped when Postgres is unreachable. `databaseURL` empty falls
+// back to TEST_DATABASE_URL, then to the global default.
+func OpenTestDatabase(t *testing.T, databaseURL string) *sql.DB {
+	t.Helper()
+
+	switch {
+	case databaseURL == "":
+		databaseURL = os.Getenv("TEST_DATABASE_URL")
+	case os.Getenv("TEST_DATABASE_URL") != "":
+		databaseURL = os.Getenv("TEST_DATABASE_URL")
+	}
+	if databaseURL == "" {
+		databaseURL = "postgres://vaultdrop:vaultdrop@localhost:5432/vaultdrop_test?sslmode=disable"
+	}
+
+	probe, err := sql.Open("postgres", databaseURL)
+	if err != nil {
+		t.Fatalf("open: %v", err)
+	}
+	if err := probe.Ping(); err != nil {
+		probe.Close()
+		t.Skipf("postgres indisponible (%v) — lancez `docker compose up postgres -d`", err)
+	}
+	probe.Close()
+
+	ensureDatabase(t, databaseURL)
+
+	resetConn, err := sql.Open("postgres", databaseURL)
+	if err != nil {
+		t.Fatalf("open: %v", err)
+	}
+	if _, err := resetConn.Exec(`DROP SCHEMA public CASCADE; CREATE SCHEMA public;`); err != nil {
+		t.Fatalf("reset schema: %v", err)
+	}
+	resetConn.Close()
+
+	if err := db.MigrateDatabase(databaseURL); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+
+	conn, err := sql.Open("postgres", databaseURL)
+	if err != nil {
+		t.Fatalf("open: %v", err)
+	}
+	if err := conn.Ping(); err != nil {
+		t.Fatalf("ping: %v", err)
+	}
+	t.Cleanup(func() { conn.Close() })
+	return conn
+}
+
+func ensureDatabase(t *testing.T, databaseURL string) {
+	t.Helper()
+	parsed, err := url.Parse(databaseURL)
+	if err != nil {
+		t.Fatalf("parse url: %v", err)
+	}
+	dbName := strings.TrimPrefix(parsed.Path, "/")
+	maintenance := *parsed
+	maintenance.Path = "/postgres"
+
+	conn, err := sql.Open("postgres", maintenance.String())
+	if err != nil {
+		t.Fatalf("open maintenance db: %v", err)
+	}
+	defer conn.Close()
+	if err := conn.Ping(); err != nil {
+		t.Fatalf("ping maintenance db: %v", err)
+	}
+
+	var exists bool
+	if err := conn.QueryRow(`SELECT EXISTS(SELECT 1 FROM pg_database WHERE datname = $1)`, dbName).Scan(&exists); err != nil {
+		t.Fatalf("check db exists: %v", err)
+	}
+	if !exists {
+		if _, err := conn.Exec(fmt.Sprintf(`CREATE DATABASE %s`, pq.QuoteIdentifier(dbName))); err != nil {
+			t.Fatalf("create database: %v", err)
+		}
+	}
+}