Use ldflags for build versioning

[kernelshard]

Problem

The version information added in #12 currently uses placeholder values. We need to inject version, commit hash, and build date at build time.

Proposed Solution

Use Go's -ldflags during build to inject version information:

go build -ldflags "-X main.Version=${VERSION} -X main.Commit=${COMMIT} -X main.BuildDate=${DATE}"

Implementation Details

• Update Makefile/build script to use ldflags
• Extract version from git tags (e.g., git describe --tags)
• Extract commit hash from git (e.g., git rev-parse HEAD)
• Generate build date (e.g., date -u +"%Y-%m-%dT%H:%M:%SZ")

Benefits

• No need to manually update version in code
• Accurate build metadata for debugging
• Follows Go best practices for versioning