[ENH] Enable LTO and Set codegen-units to 1 for Release Builds

[samadpls]

Fixes #360

[zamazan4ik]

Thank you for the PR! One question: why didn't you enable this change just in this file? Because with your variant you have the following warning in the build logs:

#17 0.173 warning: profiles for the non root package will be ignored, specify profiles at the workspace root:
#17 0.173 package:   /arch/llm_gateway/Cargo.toml
#17 0.173 workspace: /arch/Cargo.toml
#17 0.173 warning: profiles for the non root package will be ignored, specify profiles at the workspace root:
#17 0.173 package:   /arch/prompt_gateway/Cargo.toml
#17 0.173 workspace: /arch/Cargo.toml
#17 0.257    Compiling llm_gateway v0.1.0 (/arch/llm_gateway)
#17 2.886     Finished `release` profile [optimized] target(s) in 2.71s
#17 DONE 2.9s

[samadpls]

Hi @adilhafeez , could you please re-run the workflow for this PR at your convenience? This helps me update the PR accordingly.