feat: add SP616E serial LED controller driver

[MysticCodolic]

Summary

Add native serial driver support for the SP616E LED controller. The SP616E uses a
simple protocol: raw RGB pixel data followed by a 0xFF terminator byte, with no
header, checksum, or length field. Default baud rate is 115200.

This follows the same architecture as existing serial drivers (TPM2, SEDU, etc.)
with the standard ProviderSerial base class.

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's body (e.g. Fixes: #xxx[,#xxx], where "xxx" is the issue number)

Fixes: #1557

Other information:

Files Changed (4 files, +85 lines)

File	Type	Description
include/led-drivers/serial/DriverSerialSP616E.h	NEW	Header — class declaration inheriting ProviderSerial
sources/led-drivers/serial/DriverSerialSP616E.cpp	NEW	Implementation — init, writeFiniteColors, auto-registration
sources/led-drivers/schemas/schema-sp616e.json	NEW	JSON schema — output port, baud rate (115200), delay after connect
sources/led-drivers/LedDeviceSchemas.qrc	MODIFIED	Register the schema in the Qt resource file

SP616E Protocol

Property	Value
Header	None
Pixel format	Raw RGB (3 bytes per LED)
Terminator	0xFF
Frame size	(LED count × 3) + 1 bytes
Checksum	None
Default baud	115200
Default port	/dev/ttyACM0

Implementation Notes

• Follows the exact same pattern as DriverSerialTpm2 and DriverSerialSedu
• Uses _ledRGBCount for buffer sizing (dynamic, no hardcoded LED limit)
• Buffer is zero-initialized with explicit 0x00 fill
• Terminator is set once in init() and preserved across frames
  (only the RGB region is overwritten by memcpy in writeFiniteColors)
• Auto-registers via REGISTER_LED_DEVICE("sp616e", "leds_group_3_serial", ...)