feat: add settings components and persistence tests

[baba-dev]

Summary

• add a shared settings_core schema with NVS-backed storage helpers and expose new service components for UI, networking, OTA, diagnostics, connection testing, and backup export
• register the components in the build and surface an HTTP backup endpoint plus OTA/SNTP/diagnostics plumbing that relies on ESP-IDF services
• extend the host unit test harness with app_cfg persistence coverage and backup JSON serialization verification

Testing

• cmake --build tests/build --target unit_tests
• ./tests/build/unit_tests
• idf.py build (fails: command not found in container)

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https://chatgpt.com/codex/tasks/task_e_68cd143030c48324842552720f2001e7

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

[P1] Update dim timer arg when scheduling new state

The dimming timer is created only once (if (!s_dim_timer)) and the callback argument is fixed to the first settings_ui_runtime_t passed in (.arg = state). Subsequent calls with a different state reuse the same timer without updating its argument, so when the timer fires it writes dimming_active to the stale struct and may dereference freed memory if the original state has gone out of scope. Consider deleting and recreating the timer or calling esp_timer_set_arg whenever a new state is scheduled.

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