Add HMC Studio +84 Classic TKL

[Hiiwwy]

Description

Adds support for the HMC Studio +84 Classic TKL, a wired 7u Tsangan TKL PCB sold as the Nuxroskb +84 Classic TKL.

• APM32F103CBT6 using the STM32F103-compatible QMK platform
• 16 MHz external crystal, uf2boot, and a 6x17 switch matrix
• ANSI/ISO and split Backspace/right Shift layout support
• 32 WS2812 RGB underglow LEDs
• Embedded-flash wear-leveling with the final 2 KB of Flash reserved by a keyboard-specific linker script
• WS2812 startup protection to prevent the first LED from latching during reset

Tested on production hardware: keyboard input, RGB underglow, UF2 bootloader updates, and EEPROM persistence.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• N/A

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).