[Keyboard] Add Anne Pro 2D C2D support

[hitsmaxft]

Description

Adds QMK support for the Anne Pro 2D C2D revision:

• adds the HT32F52352 C2D board, linker, matrix GPIO, UART, SPI flash, and IAP configuration
• implements the AP2D BLE 2.13 UART protocol, bounded RX parser, connection state machine, slot selection, HID handshake, Caps Lock sync, and consumer reports
• moves BLE initialization, UART processing, and BLE key handling out of annepro2.c into dedicated BLE transport files
• makes the C18 BLE 2.05/2.13 compatibility choice compile-time only; C2D always selects AP2D BLE 2.13
• keeps C15/C18 external-controller RGB support unchanged

C2D direct-drive RGB is intentionally not included in this PR and will be handled separately.

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

None.

Validation

• qmk compile -kb annepro2/c18 -km default -j20
• C18 BLE 2.13 compile-time compatibility build
• qmk compile -kb annepro2/c15 -km default -j20
• qmk compile -kb annepro2/c2d -km default -j20
• host tests for both compile-time BLE report formats, BLE state transitions, AP2D slot protocol, and bounded UART parsing
• git diff --check

All builds and host-side tests pass. I do not currently have C2D hardware, so USB, matrix, BLE radio behavior, and IAP behavior have not been validated on a physical device.

qmk lint -kb annepro2/c2d still reports the existing Anne Pro 2 missing-license headers and legacy hyphenated keymap names; this PR does not modify those inherited files.

Checklist

• My code follows the code style of this project
• I have read the PR Checklist document and made the appropriate changes
• My change requires a documentation update
• 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 as well as I can manage