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.

example/pubspec.lock

@@ -502,7 +502,7 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "0.4.0"
+    version: "0.7.0"
   vector_math:
     dependency: transitive
     description: