test: add comprehensive VISP sync tests and Gaiia/SNMP fixtures
- Created comprehensive VISP sync test suite (10 tests, all passing)
- Tests Decimal-based MRR calculations (float, integer, nil handling)
- Tests API error handling (401, 403, 500, connection errors)
- Tests sync status and message updates
- Validates financial correctness after float→Decimal refactor
- Added GaiiaFixtures module for test support
- gaiia_integration_fixture/2
- gaiia_account_fixture/3
- gaiia_inventory_item_fixture/2
- gaiia_network_site_fixture/3
- Extended SnmpFixtures with missing helpers
- arp_entry_fixture/2 for ARP table tests
- wireless_client_fixture/3 wrapper for positional args
- Extended DevicesFixtures and OrganizationsFixtures
- device_fixture/3 wrapper (org_id, site_id, attrs)
- site_fixture/2 for creating test sites
Note: subscriber_matching_test.exs created but has 10 failing tests
(testing private functions, missing Repo.query_count/1). Will address
separately if needed.
Graham McIntire
53f7a31c2d