✨(agents) add Sentry instrumentation for agents

Add Sentry observability to the `agents`. Introduce a dedicated
`observability.py` module. Refactor both agents to use the shared
observability layer and extract task helpers into a new `tasks.py` module,
making task execution easier to instrument and maintain.

src/backend/meet/settings.py

@@ -1132,7 +1132,7 @@ class Base(Configuration):
         if cls.SENTRY_DSN is not None:
             sentry_sdk.init(
                 dsn=cls.SENTRY_DSN,
-                environment=cls.__name__.lower(),
+                environment=cls.__name__.lower(),  # build, test, development, production
                 release=get_release(),
                 integrations=[DjangoIntegration()],
             )