style: apply rustfmt, fix clippy warnings, and minor code cleanup

Reformat Rust code with rustfmt, suppress clippy::too_many_arguments
for Tauri IPC commands, derive Default for AppSettings, fix unused
variable pattern in TableDataView, and add unit tests for utils.

src-tauri/src/utils.rs

@@ -34,7 +34,11 @@ pub fn topological_sort_tables(
             continue;
         }
 
-        if graph.entry(parent.clone()).or_default().insert(child.clone()) {
+        if graph
+            .entry(parent.clone())
+            .or_default()
+            .insert(child.clone())
+        {
             *in_degree.entry(child).or_insert(0) += 1;
         }
     }
@@ -73,3 +77,136 @@ pub fn topological_sort_tables(
 
     result
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // ── escape_ident ──────────────────────────────────────────
+
+    #[test]
+    fn escape_ident_simple_name() {
+        assert_eq!(escape_ident("users"), "\"users\"");
+    }
+
+    #[test]
+    fn escape_ident_with_double_quotes() {
+        assert_eq!(escape_ident(r#"my"table"#), r#""my""table""#);
+    }
+
+    #[test]
+    fn escape_ident_empty_string() {
+        assert_eq!(escape_ident(""), r#""""#);
+    }
+
+    #[test]
+    fn escape_ident_with_spaces() {
+        assert_eq!(escape_ident("my table"), "\"my table\"");
+    }
+
+    #[test]
+    fn escape_ident_with_semicolon() {
+        assert_eq!(escape_ident("users; DROP TABLE"), "\"users; DROP TABLE\"");
+    }
+
+    #[test]
+    fn escape_ident_with_single_quotes() {
+        assert_eq!(escape_ident("it's"), "\"it's\"");
+    }
+
+    #[test]
+    fn escape_ident_with_backslash() {
+        assert_eq!(escape_ident(r"back\slash"), r#""back\slash""#);
+    }
+
+    #[test]
+    fn escape_ident_unicode() {
+        assert_eq!(escape_ident("таблица"), "\"таблица\"");
+    }
+
+    #[test]
+    fn escape_ident_multiple_double_quotes() {
+        assert_eq!(escape_ident(r#"a""b"#), r#""a""""b""#);
+    }
+
+    #[test]
+    fn escape_ident_reserved_word() {
+        assert_eq!(escape_ident("select"), "\"select\"");
+    }
+
+    #[test]
+    fn escape_ident_null_byte() {
+        assert_eq!(escape_ident("a\0b"), "\"a\0b\"");
+    }
+
+    #[test]
+    fn escape_ident_newline() {
+        assert_eq!(escape_ident("a\nb"), "\"a\nb\"");
+    }
+
+    // ── topological_sort_tables ───────────────────────────────
+
+    #[test]
+    fn topo_sort_no_edges() {
+        let tables = vec![("public".into(), "b".into()), ("public".into(), "a".into())];
+        let result = topological_sort_tables(&[], &tables);
+        assert_eq!(result.len(), 2);
+        assert!(result.contains(&("public".into(), "a".into())));
+        assert!(result.contains(&("public".into(), "b".into())));
+    }
+
+    #[test]
+    fn topo_sort_simple_dependency() {
+        let edges = vec![(
+            "public".into(),
+            "orders".into(),
+            "public".into(),
+            "users".into(),
+        )];
+        let tables = vec![
+            ("public".into(), "orders".into()),
+            ("public".into(), "users".into()),
+        ];
+        let result = topological_sort_tables(&edges, &tables);
+        let user_pos = result.iter().position(|t| t.1 == "users").unwrap();
+        let order_pos = result.iter().position(|t| t.1 == "orders").unwrap();
+        assert!(user_pos < order_pos, "users must come before orders");
+    }
+
+    #[test]
+    fn topo_sort_self_reference() {
+        let edges = vec![(
+            "public".into(),
+            "employees".into(),
+            "public".into(),
+            "employees".into(),
+        )];
+        let tables = vec![("public".into(), "employees".into())];
+        let result = topological_sort_tables(&edges, &tables);
+        assert_eq!(result.len(), 1);
+    }
+
+    #[test]
+    fn topo_sort_cycle() {
+        let edges = vec![
+            ("public".into(), "a".into(), "public".into(), "b".into()),
+            ("public".into(), "b".into(), "public".into(), "a".into()),
+        ];
+        let tables = vec![("public".into(), "a".into()), ("public".into(), "b".into())];
+        let result = topological_sort_tables(&edges, &tables);
+        assert_eq!(result.len(), 2);
+    }
+
+    #[test]
+    fn topo_sort_edge_outside_target_set_ignored() {
+        let edges = vec![(
+            "public".into(),
+            "orders".into(),
+            "public".into(),
+            "external".into(),
+        )];
+        let tables = vec![("public".into(), "orders".into())];
+        let result = topological_sort_tables(&edges, &tables);
+        assert_eq!(result.len(), 1);
+    }
+}