Revert "chore: Rename crate to nss"

[Not-Nik]

Reverts #35. See #27. The version can stay the same, since we will need to go back to versions > 0.7.1 when we go back to "nss" (see original PR)

[github-actions]

Clean revert of #35. Verified the diff is an exact inverse of the original rename (all 13 files, all nss ↔ nss-rs/nss_rs references), with the intentional exception of keeping the version at 0.8.0 rather than reverting to 0.3.0 — which makes sense given the crates.io versioning constraint noted in the PR description.

The tests/init.rs module rename (nss_init → nss) is correct: the name conflict that motivated renaming it in #35 no longer exists now that the crate is back to nss_rs.

CI is green across all completed checks (sanitizers, format, deny, dependency-review, multiple platform/toolchain combos); a few clippy/Windows jobs are still in progress.

One minor pre-existing issue flagged inline (src/sig.rs stale import) — non-blocking since the file is dead code.