fix(docker): touch src/main.rs to force recompilation in cache layer

[denerFernandes]

The dependency-cache layer removes the binary and fingerprints, but cargo's incremental detection still considers the crate up-to-date when the real sources are COPYed in the next layer. This resulted in a 580KB dummy binary (from the 'fn main(){}' stub) being shipped instead of the real 15MB proxy binary.

Adding 'touch src/main.rs' before the final cargo build forces cargo to recompile the turbineproxy crate.

Summary

Type of Change

• feat — new feature
• fix — bug fix
• perf — performance improvement
• refactor — code change without feat/fix
• docs — documentation only
• test — adding or updating tests
• ci — CI/CD changes
• chore — maintenance

Related Issue

Closes #

Checklist

• Commit messages follow Conventional Commits
• cargo fmt --all passes
• cargo clippy --all-targets -- -D warnings passes
• Tests added or updated for logic changes
• cargo test --lib passes locally
• Documentation updated (if applicable)

Testing