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>

.env.example

@@ -24,7 +24,7 @@ POSTGRES_DB=mangalord
 DATABASE_URL=postgres://mangalord:mangalord@postgres:5432/mangalord
 BIND_ADDRESS=0.0.0.0:8080
 STORAGE_DIR=/var/lib/mangalord/storage
-RUST_LOG=info,mangalord=debug
+RUST_LOG=info,mangalord=debug,chromiumoxide::conn=off,chromiumoxide::handler=off
 
 # ----- Auth / cookies -----
 # COOKIE_SECURE controls whether the `Secure` flag is set on the session