fix(button): handle GPIO ISR service installation idempotency

[iyassou]

Description

The GPIO ISR service installation is idempotent per ESP-IDF documentation. ESP_ERR_INVALID_STATE indicates the service was already installed by another component, so not a fatal error. This change allows iot_button to coexist with
other components that install the ISR service first by treating ESP_ERR_INVALID_STATE as success in button_gpio_set_intr. The existing isr_service_installed static flag is retained to avoid redundant calls after initial installation.

Related

No similar issues have been raised to my knowledge.

Testing

I haven't ran the test suite.

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Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

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