test: enhance test coverage to 99% (#8)

[pike00]

Resolves #8.

Summary of Changes

• Increased unit test coverage across custom_components/tryfi and underlying pytryfi library from 79% to 99%.
• All 194 unit tests pass cleanly.

Key Additions

• Integration Core & Services: Added full test coverage for custom service calls (set_led_color, turn_on_led, turn_off_led, set_lost_mode, set_wifi_location), setup/unload lifecycles, and device removal filters in tests/test_init.py and tests/test_services.py.
• pytryfi Models: Created unit tests for FiUser, FiWifiNetwork, and ledColors, and expanded coverage for FiPet and FiDevice.
• API Queries: Added tests for GraphQL payload formatting and error handling in test_query.py and test_pytryfi.py.
• Entities: Covered fallback and missing attribute states across binary_sensor, device_tracker, sensor, and switch.

(Written with antigravity, I had some tokens to burn so I thought i'd contribute to a project I use and has relatively active development!)