feat(test+pages): 补充测试文件和缺失业务页面 (Issue #24)
补充内容：
- 5个测试文件: water_data_model_test, auth_service_test, home_page_test, login_page_test, constants_test
- 4个业务文件: inspection_tasks_page, revenue_page, water_service, custom_card
解决PM审核问题：
- 补充 test/ 目录下的单元测试和Widget测试
- 补齐home_page引用的巡检和营收页面
- 补齐water_monitoring_page引用的water_service和custom_card
by bot_qa
