diy: add M5StickS3 support

[BitromNO]

Summary

Adds support for the M5Stack M5StickS3 (ESP32-S3, N8R8, ST7789P3 135x240 IPS LCD, two buttons, 120mAh battery) as a DIY board, using the existing CUSTOM board option.

What changed

• main/Kconfig.projbuild: new HAS_M5PM1 option (depends on BOARD_TYPE_CUSTOM) selecting the M5PM1 PMIC driver.
• main/power.c: dispatch to power/m5pm1.inc when CONFIG_HAS_M5PM1.
• main/power/m5pm1.inc: new M5PM1 (I2C 0x6E, SDA=G47/SCL=G48) driver. The StickS3 uses the M5PM1 rather than AXP/IP5306. Critical detail: the PMIC's PYG2 output (active high) gates the L3B rail that powers the LCD/backlight, so the driver asserts PYG2 in power_init() and drives it from power_screen_on(). Register writes are best-effort (boot continues even if the PMIC is unresponsive) and the driver disables the PMIC i2c idle-sleep timeout + watchdog.
• configs/sdkconfig_display_m5sticks3.defaults: build profile (SPI display pins, buttons, octal PSRAM, TinyUSB CDC).
• gitlab/diy_fw.yml: build_diy_display_m5sticks3 CI job.
• diy/README.md: hardware entry.

Notes

• USB VID/PID is 303a:4001 (ESP32-S3 native USB) - differs from retail Jade, so custom Electrum/HWI builds are required until added (documented in diy/README.md, same as T-Display S3).
• As a custom-board build the OTA board type reports UNKNOWN; hardware detection is unaffected.
• Not wired up: battery voltage/charging reporting (M5PM1 battery register offsets not yet pinned out) and the speaker amp (PYG3 held off).

Testing

Verified on hardware: display (ST7789P3 135x240), both buttons, USB wallet pairing with Blockstream Green and Sparrow, BLE pairing with the iPhone Blockstream Green app. Boot logs confirm M5PM1 registers (DEVICE_ID 0x50, MODE 0x0c, OUT 0x04 = PYG2 high/L3B on).