ci: regenerate uv.lock on release and backfill to 1.6.1

semantic-release bumped only pyproject.toml, leaving uv.lock's project
version stale (drifted to 1.6.0 while the project was at 1.6.1). Add
'uv lock' as the build_command and include uv.lock in the release commit
via assets so the lockfile stays in sync on every release. Also backfill
the current uv.lock to 1.6.1.

Author: marcinpsk

pyproject.toml

@@ -70,7 +70,8 @@ fail_under = 96
 [tool.semantic_release]
 version_toml = ["pyproject.toml:project.version"]
 commit_message = "chore(release): v{version}"
-build_command = ""
+build_command = "uv lock"
+assets = ["uv.lock"]
 
 [tool.semantic_release.changelog]
 template_dir = "templates"