Adds 42 Vitest unit tests for the two composables extracted from the
admin categories page in ERP-50.

- useCategoriesAdmin (14 tests): fetchAll/fetchTypes, includeDeleted toggle,
  loading flags, error handling, reset, singleton sharing.
- useCategoryForm (28 tests): validation rules RG-1.02/1.04/1.05, trim,
  POST/PATCH/DELETE wiring, 409 (RG-1.07) and 422 violation mapping,
  isDirty, loadFrom, reset, instance isolation.

Mocks useApi/useI18n/useToast via vi.stubGlobal and ~/shared/stores/auth
to keep the suite hermetic (no backend required).

@@ -0,0 +176,4 @@
+            expect(types.value).toEqual([TYPE_VENTE, TYPE_ACHAT])
+        })
+
+        it('peuple error.value et vide types en cas d echec', async () => {

@@ -0,0 +10,4 @@
+const mockToastSuccess = vi.hoisted(() => vi.fn())
+const mockToastError = vi.hoisted(() => vi.fn())
+
+vi.stubGlobal('useApi', () => ({

@@ -0,0 +130,4 @@
+            expect(form.errors.value.name).toBe('admin.categories.validation.nameLength')
+        })
+
+        it('signale erreur si name fait 121 caracteres (> 120, RG-1.04)', () => {

@@ -0,0 +232,4 @@
+            // La cle est interpolee avec le nom soumis : on retrouve "Vis" dans
+            // les params i18n (stub serialise les params).
+            expect(form.errors.value.name).toContain('admin.categories.toast.duplicate')
+            expect(form.errors.value.name).toContain('"name":"Vis"')

@@ -0,0 +280,4 @@
+            await form.submitCreate()
+
+            expect(form.errors.value.categoryType).toBe('Type invalide.')
+        })

@@ -0,0 +282,4 @@
+            expect(form.errors.value.categoryType).toBe('Type invalide.')
+        })
+
+        it('fallback en erreur globale + toast si le status n est ni 409 ni 422', async () => {

@@ -0,0 +388,4 @@
+            expect(result).toBeNull()
+            expect(form.errors.value.name).toContain('admin.categories.toast.duplicate')
+            expect(form.errors.value.name).toContain('"name":"Doublon"')
+        })