fix(ci): tests unitaires Vitest uniquement, sans Playwright ni migrations

Les tests migration exigent un schéma aligné via db push (hors scope CI).
Trois fichiers unitaires importaient @playwright/test par erreur.

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/tests/unit/embedding-validation.test.ts

@@ -1,4 +1,4 @@
-import { test, expect } from '@playwright/test'
+import { describe, test, expect } from 'vitest'
 import { validateEmbedding, calculateL2Norm, normalizeEmbedding } from '../../lib/utils'
 
 test.describe('Embedding Validation', () => {