docs: fix build commands from repository root

[jacktony2001]

Summary

The repository's build instructions currently omit the required aether working directory even though the root checkout has no Cargo.toml.

This PR:

• Adds cd aether before build commands in the English and Persian README files.
• Corrects the documented binary path to aether/target/release/aether when commands are run from the repository root.
• Adds the same working-directory clarification to the detailed English and Persian library-build documentation.

Why

Following the previous root-level instructions from a fresh checkout leads users to invoke Cargo without a manifest. The corrected commands match the actual repository layout and the Dockerfile's existing /usr/src/app/aether working directory.

Validation

• git diff --check passes.
• Confirmed the only Rust manifests are under aether/ and quiche/.
• Confirmed this PR changes documentation only.
• A full Cargo build was not run in the validation environment because Rust/Cargo is not installed there.

Closes #83