feat: add T-Deck MAX board foundation

[liurbinbin]

Summary

This PR adds the T-Deck MAX board foundation, including the MAX variant, XL9555 support, and shared I2C initialization.

Scope

• Add the T-Deck MAX PlatformIO variant and Arduino pin definitions.
• Add the MAX board layer and XL9555 access layer.
• Add MAX board initialization, sleep isolation, hardware-model fallback, and shared I2C scan handling.
• Select the charger macro and I2C address according to the confirmed physical board revision.

Hardware gate

• SY6970 boards use XPOWERS_CHIP_SY6970 and address 0x6A.
• The submitted macro and address must match the physical charger IC.

Exclusions

This PR does not enable BHI260AP, LTR553ALS, A7682E, ES8311, MAX touch keys, keyboard controls, antenna switching, or motor routing.

Dependencies

None.

🤝 Attestations

• [√ ] I have tested that my proposed changes behave as described.
• [√ ] I have tested that my proposed changes do not cause any obvious regressions on the following devices:
  • [√ ] LilyGo T-Deck-Max
  • [√ ] LilyGo T-Deck-ProV1_1

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[liurbinbin]

Currently fixing CI build errors, will update within 24 hours.

[liurbinbin]

目前正在修复CI构建错误，24小时内会更新。

Some issues surfaced after PR splitting.