chore: satisfy CI fmt/clippy gates; make the release publish step idempotent

`cargo fmt --all -- --check` and `cargo clippy --all-targets -- -D warnings` are
CI gates and both were failing on this release's code.

- rustfmt across the files touched by the release
- `.split('/').last()` walks the whole iterator on a DoubleEndedIterator; use
  `.next_back()` (4 sites in the setup/featured + delete handlers)
- `set_progress` had two identical branches; the intent is "take the first
  reading, then only move forward", which is one condition

release.yml published unconditionally on a version tag, so a version already on
crates.io (released by hand, or a re-run of the job) failed the workflow — a
version can never be re-uploaded. It now checks the registry and skips instead.

.github/workflows/release.yml

@@ -21,9 +21,20 @@ jobs:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
       - uses: Swatinem/rust-cache@v2
+      # Skip when this version is already on crates.io — a version can never be
+      # re-uploaded, so publishing one that exists (released by hand, or a re-run
+      # of this job) is a guaranteed failure rather than a real problem.
       - name: Publish to crates.io
         if: ${{ env.CARGO_REGISTRY_TOKEN != '' }}
-        run: cargo publish
+        run: |
+          name=$(cargo metadata --no-deps --format-version 1 | jq -r '.packages[0].name')
+          version=$(cargo metadata --no-deps --format-version 1 | jq -r '.packages[0].version')
+          if curl -sf -H 'User-Agent: cortiq-gateway-release' \
+               "https://crates.io/api/v1/crates/$name/$version" >/dev/null; then
+            echo "$name $version is already published — skipping"
+          else
+            cargo publish
+          fi
 
   # --- prebuilt binaries + GitHub Release -----------------------------------
   release: