🐛 fix(duckdb): 修复唯一索引识别与多库对象解析

- 合并 DuckDB 约束与索引元数据，恢复唯一索引表的可编辑判定
- 修复 attach 多库场景下 catalog/schema/table 定位混乱问题
- 统一前后端 qualified name 解析，支持带点和带引号对象名
- 补充 DuckDB 元数据与编辑链路回归测试

internal/app/db_context_test.go

@@ -140,6 +140,21 @@ func TestNormalizeSchemaAndTable_OceanBaseOracleUsesSchemaFromDatabaseTree(t *te
 	}
 }
 
+func TestNormalizeSchemaAndTable_DuckDBPreservesQuotedQualifiedName(t *testing.T) {
+	t.Parallel()
+
+	schemaOrDb, table := normalizeSchemaAndTable(connection.ConnectionConfig{
+		Type: "duckdb",
+	}, `"analytics.catalog"."main.schema"`, `"daily.events"."2026.06"`)
+
+	if schemaOrDb != `"analytics.catalog"."main.schema"` {
+		t.Fatalf("expected duckdb dbName/catalog path preserved, got %q", schemaOrDb)
+	}
+	if table != `"daily.events"."2026.06"` {
+		t.Fatalf("expected duckdb qualified table preserved, got %q", table)
+	}
+}
+
 func TestQuoteTableIdentByType_KingbaseNormalizesQuotedQualifiedTable(t *testing.T) {
 	t.Parallel()