Each character in the Base62 string maps to a number: 0–9 → 0–9, A–Z → 10–35, a–z → 36–61.
Characters are combined into one BigInt number by repeatedly multiplying by 62 and adding each digit's value (base-62 to decimal).
The big number is converted back to bytes by taking mod 256 and dividing — reversing the encoding's base-256 process.
Bytes are decoded as UTF-8 text using TextDecoder. If it's not valid UTF-8, the raw hex values are shown instead.