Upgrade to Zig 0.16.0, switch changelog tooling to changie, and add resource generation field

[Boomatang]

Summary

• Upgrades Zig from 0.15.x to 0.16.0 and updates all source code to match the new standard library API (new main signature with std.process.Init, std.Io-based I/O, std.process.run, @EnumLiteral(), etc.)
• Bumps zig-clap from 0.11.0 to 0.12.0 and zig-sqlite from v0.3.2 to v0.4.0
• Replaces towncrier with changie for changelog management, adding platform-specific changie binaries as lazy build dependencies and exposing changie:version, changie:add, changie:batch, and changie:merge build steps
• Adds the Kubernetes generation metadata field to the Metadata struct, JSON output, and SQLite schema
• Removes boilerplate comments from build.zig and simplifies release staging directory handling
• Updates README with the new changie-based developer workflow and release process