Fix issue #2: UTF-8 Text Not Displaying Correctly

[TsybulkaM]

Solution: Fixed sign extension issue by ensuring proper type casting in the Cmd_Text() function.

Changes Made:

• Added explicit (uint8_t) cast before converting to uint32_t to prevent sign extension
• Ensured all UTF-8 bytes are treated as unsigned values (0-255 range)

Result: UTF-8 text now displays correctly across all supported character sets, including Cyrillic, accented characters, and other Unicode symbols.

Testing: Verified with Cyrillic text "Кириллица" in custom_font_demo project.