fix: phase 1 bugs — CSS tokens, pluralization, error handling, cross-platform tests

- Add missing --space-1 CSS token used by filter and detail components

- Fix active nav link losing styles on hover (CSS specificity)

- Correct Russian day pluralization (21 день, 22 дня, 25 дней)

- Show filter error banner even when stale race data is present

- Add cross-env for Windows-compatible npm test

- Add global JSON error handler in Express for malformed request bodies

- Replace stateless mock DB with in-memory store for correct DELETE/UPDATE behavior

Made-with: Cursor

backend/src/db.ts

@@ -69,6 +69,8 @@ function createMockPool(): Pool {
       fields: [],
     }) as QueryResult<T>;
 
+  const store = new Map<string, RaceRow>();
+
   const mockQuery = async <T extends QueryResultRow>(
     text: string,
     params?: unknown[],
@@ -76,11 +78,9 @@ function createMockPool(): Pool {
     const sql = text.replace(/\s+/g, " ").trim();
     const p = params ?? [];
 
-    if (sql.includes("DELETE FROM races")) {
-      return emptyResult();
-    }
     if (sql.includes("INSERT INTO races") && sql.includes("RETURNING")) {
       const row = mockRowFromInsert(text, p);
+      store.set(row.id, row);
       return {
         rows: [row as unknown as T],
         rowCount: 1,
@@ -89,12 +89,49 @@ function createMockPool(): Pool {
         fields: [],
       } as QueryResult<T>;
     }
+
+    if (sql.includes("DELETE FROM races")) {
+      const id = String(p[0] ?? "");
+      const existed = store.delete(id);
+      return {
+        rows: [],
+        rowCount: existed ? 1 : 0,
+        command: "DELETE",
+        oid: 0,
+        fields: [],
+      } as QueryResult<T>;
+    }
+
     if (sql.includes("UPDATE races") && sql.includes("RETURNING")) {
-      return emptyResult();
+      const id = String(p[p.length - 1] ?? "");
+      const existing = store.get(id);
+      if (!existing) {
+        return emptyResult();
+      }
+      const updated = { ...existing, updated_at: new Date().toISOString() };
+      store.set(id, updated);
+      return {
+        rows: [updated as unknown as T],
+        rowCount: 1,
+        command: "UPDATE",
+        oid: 0,
+        fields: [],
+      } as QueryResult<T>;
     }
+
+    if (sql.includes("SELECT * FROM races WHERE id =")) {
+      const id = String(p[0] ?? "");
+      const row = store.get(id);
+      return row
+        ? { rows: [row as unknown as T], rowCount: 1, command: "SELECT", oid: 0, fields: [] } as QueryResult<T>
+        : emptyResult();
+    }
+
     if (sql.includes("SELECT * FROM races")) {
-      return emptyResult();
+      const rows = Array.from(store.values());
+      return { rows: rows as unknown as T[], rowCount: rows.length, command: "SELECT", oid: 0, fields: [] } as QueryResult<T>;
     }
+
     return emptyResult();
   };