chore(russh): bump russh-sftp dev-dependency 2.1.0 → 2.3.0

[Yaminyam]

Summary

Bump the russh-sftp dev-dependency used by the sftp_client / sftp_server examples from 2.1.0 to 2.3.0.

Why

The 2.1.0 → 2.3.0 window includes the merged perf fix from AspectUnk/russh-sftp#83 — routing SFTP WRITE/DATA payloads through serde_bytes instead of the generic VecVisitor path, ~+29% throughput on large transfers. Examples in this repo should track the version downstream users actually consume.

Change

One-line bump in russh/Cargo.toml:

 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
-russh-sftp = "2.1.0"
+russh-sftp = "2.3.0"

Test plan

• cargo build -p russh --example sftp_client --example sftp_server → builds clean, no source changes needed (no breaking changes in russh-sftp 2.1 → 2.3 for the API surface these examples use).

[Yaminyam]

The CI failures here are unrelated to this dev-dependency bump — they come from a transitive dsa breakage in the ssh-key = "=0.7.0-rc.10" line:

error[E0599]: no function or associated item named `generate` found for struct `dsa::Components`
error[E0599]: no function or associated item named `generate` found for struct `dsa::SigningKey`
error: could not compile `ssh-key` (lib) due to 2 previous errors

ssh-key itself is pinned with =, but its transitive dsa dependency is a caret range. A newer dsa rc removed/renamed Components::generate / SigningKey::generate, so ssh-key 0.7.0-rc.10 no longer compiles once the lockfile picks up the newer dsa. The russh-sftp dev-dep bump in this PR just triggered a lockfile re-resolution that surfaced it.

This is already addressed upstream: main/v0.62.0 moved to ssh-key = "=0.7.0-rc.11", which tracks the new dsa API. Rebasing this PR onto v0.62.0 (or bumping the ssh-key pin to rc.11) should turn CI green.

[Yaminyam]

Rebased onto main (now at v0.62.1, which uses ssh-key = "=0.7.0-rc.11"). cargo check -p russh passes locally — the dsa/ssh-key compile error is resolved. Ready for a CI re-run.

[Eugeny]

Thank you!