G5: F19 — replace deprecated get_event_loop with get_running_loop

Why: asyncio.get_event_loop() inside an async function emits
DeprecationWarning since Python 3.10 and raises in some contexts on
Python 3.12+. The call in CommandHandlerBase.send() is always inside
a running async context where get_running_loop() is the correct API.

Refs: Forensics report finding F19

src/meshcore/commands/base.py

@@ -185,7 +185,7 @@ class CommandHandlerBase:
             futures: List[asyncio.Future] = []
             subscriptions = []
 
-            loop = asyncio.get_event_loop()
+            loop = asyncio.get_running_loop()
             for event_type in expected_events:
                 future = loop.create_future()