3.6 Story 3-6: Test Frontend Services and Utils

Sprint Key: 3-6-test-frontend-services-and-utils Epic: 3 PRD: testing-framework

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Story 3-6: Test Frontend Services and Utils

Status: ready-for-dev

Story

As a developer, I want unit tests for all untested frontend services and utilities, So that HTTP interactions and utility logic are verified without API dependencies.

Acceptance Criteria

1. AC1: adminDashboardService — test all 11 async methods + 2 utility functions with mocked httpService
2. AC2: fileService — test file operations including FormData upload
3. AC3: labelService — test full CRUD cycle
4. AC4: userService — test singleton with GDPR-critical deleteAccount
5. AC5: databaseOperationsService — test backup/restore/optimize HTTP calls
6. AC6: ThemeManager — test theme switching, singleton, DOM interactions
7. AC7: fileUtils — test file size formatting, MIME type checking
8. AC8: store/index.js — test Vuex store initialization and localStorage plugin
9. AC9: Regression safety — all existing tests pass, zero lint errors