Function textToBraille

Convert a text string to braille literary characters (Grade 1 alphabet). Used for instrument abbreviations in ensemble scores.

• Letters (a-z, A-Z) are converted to braille lowercase (case-insensitive)
• Digits (0-9) are converted to braille digits with number sign prefix
• Spaces become braille blank cells
• Periods (.) become dot 3 (abbreviation period)
• Other characters are skipped