- service/auth/login.rs: extract auth_find_user() helper combining
username + email lookup, reducing login flow from 5 levels to 3
- etcd/register.rs: extract run_keep_alive_stream() and
renew_lease_and_reregister() from spawn_keep_alive(), reducing
max nesting from 7 levels to 3
- cache/lru.rs: replace lock().unwrap() with if let Ok guard,
consistent with other lock acquisitions in the same file
- service/repo/core.rs: replace try_into().unwrap() with
copy_from_slice which is infallible for fixed-size slices
- service/auth/rsa.rs: replace 3 expect() calls with map_err()
for ChaCha20Poly1305 key init and session key retrieval
- config/mod.rs: replace GLOBAL_CONFIG.get().expect() with
unwrap_or_else fallback to empty config
zhenyi