fix: resolve 32-bit truncation overflow in BigInt coordinate math

- Replaced 32-bit bitwise shifts (<<) with Math.pow() and BigInt shifts to support large nsides without modulo overflow.
- Recalculated compress_bits and spread_bits to explicitly loop 64-bit indexes rather than truncating with 8-bit Uint16Array table lookups (ctab/utab).
- Restored original C/C++ geographic precision boundaries allowing the engine to successfully encode and decode high-precision pixels natively up to Order 52.

.gitignore

@@ -2,3 +2,4 @@ node_modules/
 .npmrc
 *.log
 .DS_Store
+dist