feat(audit): full-history JSONL export in the actions menu

The menu so far only exported the current view (type + search
filter over the page 100-event window). A second action now fetches
the complete event history of the active project scope in one
EventLog call (the RPC has no cursor and no server-side cap) and
writes it as JSONL. Serialisation extracted to a top-level function
with unit tests; a stale comment advertising the never-shipped
"chain audit export" command now names "chain admin events --json".
Studio 0.73.0.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/data/about_info.dart

@@ -4,7 +4,7 @@
 
 /// Studio's own build version. Bump on every UI release so the
 /// running app self-identifies.
-const String kStudioVersion = '0.72.1';
+const String kStudioVersion = '0.73.0';
 
 const String kProductName = 'Ch∆In Studio';
 const String kVendorName = 'Flemming.AI (F∆I)';