refactor: mantener única DB por suite y limpiar tablas en beforeEach

Co-authored-by: aider (openrouter/openai/gpt-5) <aider@aider.chat>

tests/unit/tasks/service.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, beforeEach, afterEach } from 'bun:test';
+import { describe, it, expect, beforeEach, afterEach, beforeAll, afterAll } from 'bun:test';
 import { Database } from 'bun:sqlite';
 import { initializeDatabase, ensureUserExists } from '../../../src/db';
 import { TaskService } from '../../../src/tasks/service';
@@ -6,17 +6,23 @@ import { setDb, resetDb } from '../../../src/db/locator';
 
 let memDb: Database;
 
-beforeEach(() => {
+beforeAll(() => {
   memDb = new Database(':memory:');
   initializeDatabase(memDb);
   setDb(memDb);
 });
 
-afterEach(() => {
-  try {
-    resetDb();
-    memDb.close();
-  } catch {}
+afterAll(() => {
+  try { resetDb(); memDb.close(); } catch {}
+});
+
+beforeEach(() => {
+  // Reafirmar el locator y limpiar tablas relevantes entre tests
+  setDb(memDb);
+  try { memDb.exec('DELETE FROM task_assignments'); } catch {}
+  try { memDb.exec('DELETE FROM tasks'); } catch {}
+  try { memDb.exec('DELETE FROM users'); } catch {}
+  try { memDb.exec('DELETE FROM groups'); } catch {}
 });
 
 describe('TaskService.listGroupUnassigned / countGroupUnassigned', () => {