[BE-40] Write e2e tests for the full asset CRUD flow in opsce module

[yusuftomilola]

Problem

The asset management flow has no end-to-end tests. It is not possible to verify the full request-response cycle (auth → create asset → update → transfer → delete) without manual testing.

Proposed Solution

Create backend/test/opsce-assets.e2e-spec.ts using Supertest and an in-memory SQLite test database. The test suite should cover the full asset lifecycle.

Acceptance Criteria

• Setup creates a test app with an in-memory database and seeds a test user (ADMIN role)
• POST /api/auth/login — returns 200 with tokens for valid credentials
• POST /api/assets — returns 201 with created asset, returns 401 without token
• GET /api/assets — returns paginated list with the created asset
• PATCH /api/assets/:id — updates fields and returns updated asset
• POST /api/assets/:id/transfer — changes assignee and verifies audit log entry
• DELETE /api/assets/:id — soft-deletes asset, asset absent from subsequent list
• Database is reset between each test to ensure isolation