0.8.0: pretty logger (Log) + crash capture

- Log: static entry + scoped Loggers (Log.tag), six levels, lazy messages,
  structured fields, ANSI ConsoleSink, DeveloperSink, MemorySink, NoopSink.
  Sinks compose via +; throwing sinks are isolated.
- Log.configure wires FlutterError/PlatformDispatcher/isolate errors through
  Log.e by default; log-then-rethrow deduped via Expando.
- UxKeyboard: migrate kDebugMode print() to Log.tag('KB').d lazily.
- Depend on package:clock for testable timestamps.

lib/ux.dart

@@ -12,4 +12,5 @@ export 'src/file.dart';
 export 'src/keyboard.dart';
 export 'src/auto_map.dart';
 export 'src/sensor.dart';
-export 'src/functional.dart';
+export 'src/functional.dart';
+export 'src/log.dart';