fix: remove prototype mutations that cause TypeError in sandboxed environments

[Copilot]

Summary

Fixes #403: TypeError: Cannot assign to read only property 'toString' of object '#<Object>'

In sandboxed environments that block prototype mutation (e.g. n8n 2.x Code nodes), require('node-firebird') throws a TypeError because two pieces of code try to mutate prototypes during initialization.

Root Causes

1. long npm package — The long dependency mutates Long.prototype.toString (and other Long.prototype methods) during module initialization. In sandboxed environments where prototype mutation is blocked, this fails with TypeError: Cannot assign to read only property 'toString' of object '#<Object>'.

2. String.prototype.padLeft polyfill in lib/index.js — Similarly mutates String.prototype, which fails in the same sandboxed environments.

Changes

lib/wire/serialize.js

• Removed require('long')
• addInt64: replaced Long.fromNumber(value) + writeInt32BE with Buffer.writeBigInt64BE(BigInt(Math.trunc(value))) — consistent with the existing addInt128 approach
• readInt64: replaced new Long(low, high).toNumber() with Buffer.readBigInt64BE() — consistent with the existing readInt128 approach
• Added comments documenting the pre-existing precision limitation for values outside Number.MAX_SAFE_INTEGER (same behaviour as the previous Long implementation)

lib/index.js

• Removed the String.prototype.padLeft polyfill block

lib/utils.js

• Replaced .padLeft(n, c) calls with the native .padStart(n, c) (ES2017, already used elsewhere in the codebase)

package.json / package-lock.json

• Removed long from dependencies

Testing

All tests that passed before continue to pass. Test failures are unchanged (all pre-existing Connect error failures due to no Firebird server in CI).