fix(crawler): unhang shutdown on lingering Arc<Browser>, silence WS noise (0.43.1)

- Handle::close aborts its chromiumoxide driver task when another
  Arc<Browser> outlives the call, so shutdown returns instead of
  hanging on a stream that never terminates. Generic close_or_abort
  helper with regression tests covering both Arc paths.
- daemon.shutdown() is wrapped in a 5s timeout in main as defense
  in depth.
- Default RUST_LOG silences chromiumoxide::conn / chromiumoxide::handler
  WS-deserialize ERROR spam.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mangalord"
-version = "0.43.0"
+version = "0.43.1"
 edition = "2021"
 default-run = "mangalord"