Improve crewai run startup UX (#6297)

Remove redundant startup logs from `crewai run` and make the legacy flow
command warning actionable.

- Stop printing `Running the Flow` and `Running the Crew` before project
  execution.
- Stop printing the redundant `Flow started with ID: ...` line while
  preserving flow lifecycle event emission.
- Replace Click's generic `kickoff` deprecation warning with a clearer
  message that tells users to use `crewai run`.

lib/cli/tests/test_cli.py

@@ -190,7 +190,10 @@ def test_flow_kickoff_is_deprecated_and_uses_run_path(run_crew, runner):
         definition=None,
         inputs=None,
     )
-    assert "DeprecationWarning" in result.output
+    assert (
+        "The command 'crewai flow kickoff' is deprecated. Use 'crewai run' instead."
+        in result.output
+    )
 
 
 @mock.patch("crewai_cli.create_json_crew.create_json_crew")