feat(hub): default to live hub on startup + accept partial flow bags

Two small changes that together get Recl∆Im out of demo mode
on the very first launch after a flow.completed event lands:

  1. HubSettings.useHub defaults to true. New installs and
     post-reset launches probe the hub straight away; if the
     probe fails (no hub running, wrong port, auth denied),
     the existing graceful fallback in main.dart drops back to
     MockRepository. A user can still flip useHub off via the
     Hub-Reiter.

  2. HubRepository._parse now only requires the 'norm' key to
     consider an event 'Recl∆Im-shaped'. SKM, benefit and
     frust default to zero if absent; tier_lowest falls back to
     the cohort source's tier. This makes the partial bag
     produced by flows/durchstich-from-file.yaml — which can
     run without econ.skm_score's nested-input gymnastics —
     enough to surface a real heatmap point.

Wired together: launch the app while chain serve runs and at
least one flow.completed event is in the audit log → the
Heatmap-Tab shows that norm live, with its tier and norm-title
parsed from the actual audit-log JSON instead of Fixtures.

Signed-off-by: flemming-it <sf@flemming.it>

app/lib/data/hub_endpoint.dart

@@ -49,7 +49,7 @@ class HubSettings {
       port: prefs.getInt(_kPort) ?? defaultPort,
       secure: prefs.getBool(_kSecure) ?? false,
       authToken: prefs.getString(_kToken),
-      useHub: prefs.getBool(_kUseHub) ?? false,
+      useHub: prefs.getBool(_kUseHub) ?? true,
     );
   }