fix: strdup ObjC strings returned across CGo boundary

UTF8String pointers into NSString buffers become dangling once the
autorelease pool drains. Use strdup so callers own the memory, and
pair each call site in Go with C.free via defer.

Affected: getSystemInfo, getNSHomeDirectory, getNSCacheDirectory.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

chore: bump version

chore: bump version

chore: bump version

chore: bump version

chore: bump version

ci: allow notarization to run on workflow_dispatch

chore: bump version

chore: bump version

chore: bump version to 4.1.2