A run says whether the dashboard, the CLI or a script asked for it

`POST /runs/flows/{name}` hardcoded `cause: "api"`, so every row in the
history claimed the same origin. The body now carries an optional `cause`,
closed to the values the column knows — the dashboard sends nothing and stays
"api", `fluksio run` says "cli", and the SDK client says "sdk".

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013Gf7WaExcJ9bs3kfJXB3nK

backend/fluksio/sdk/cli.py

@@ -459,7 +459,11 @@ def cmd_run(args: argparse.Namespace, rest: list[str]) -> int:
             ):
                 params = _ask_params(definition)
             handle = client.submit(
-                args.flow, params, seed=args.seed, no_cache=args.no_cache
+                args.flow,
+                params,
+                seed=args.seed,
+                no_cache=args.no_cache,
+                cause="cli",
             )
             _say(f"{handle.id}  queued  {json.dumps(params)}")
             if not wait: