支持 S3 兼容对象存储 (#336)

* feat(storage): 支持 S3 对象存储

* fix(storage): 补齐 S3 对象文件后缀

backend/cmd/migrate-sqlite-postgres/main_test.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"sync"
+	"testing"
+
+	"infinite-canvas/backend/internal/database"
+
+	"gorm.io/gorm/schema"
+)
+
+func TestMigrationListCoversSchemaModels(t *testing.T) {
+	want := make(map[string]bool, len(database.Models()))
+	cache := &sync.Map{}
+	for _, value := range database.Models() {
+		parsed, err := schema.Parse(value, cache, schema.NamingStrategy{})
+		if err != nil {
+			t.Fatal(err)
+		}
+		want[parsed.Table] = false
+	}
+	for _, migration := range migrations() {
+		if _, exists := want[migration.name]; !exists {
+			t.Fatalf("migration list contains unknown table %q", migration.name)
+		}
+		if want[migration.name] {
+			t.Fatalf("migration list contains duplicate table %q", migration.name)
+		}
+		want[migration.name] = true
+	}
+	for table, covered := range want {
+		if !covered {
+			t.Errorf("migration list is missing table %q", table)
+		}
+	}
+}