Put the deployment-only dependencies behind a server extra

A data-science environment installing fluksio waited for lxml, aiohttp and
the rest of a connector stack it has nothing to talk to. Outbound mail,
error reporting and the MQTT and InfluxDB clients moved to
`fluksio[server]`, which the image installs; each import is guarded and
names the extra. `tenacity` had no import site at all and is gone.

23 fewer packages and the compiled ones among them — a bare `pip install
fluksio` still serves, runs every python node, and registers the mqtt and
influxdb node types, which only need the library when one is actually
built. sentry-sdk arrives anyway underneath `fastapi[standard]`; what
changed there is that nothing of ours requires it.

The dev environment keeps every extra: the suite exercises the connectors
and strict mypy checks their call sites.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019Hra4ndWMCLU5F3KjUuVAc

worker/fluksio_worker/worker_main.py

@@ -89,6 +89,10 @@ def _emit(event: dict[str, Any]) -> None:
 class _Reporter(ModuleType):
     """``import fluksio`` — the parts of a node's job that need the engine."""
 
+    #: The same name the SDK exports at top level, so a node written against
+    #: one surface finds it on the other. Set by ``_install_reporter``.
+    logger: logging.Logger
+
     def emit(self, **ports: Any) -> None:
         """Publish on this node's output ports without returning yet.