feat(advice): LLM brewing advice on every observation (work in progress)

Stores a model's advice for each recorded reading, in its own field, so the
brewer's own comment is never overwritten.

Fire and forget: the advice is generated in a background thread, so
recording a reading never blocks on the model.  A failure is recorded as a
visible note saying the advice could not be generated, because a silent
failure is indistinguishable from "still thinking".

The model is `glm-5.3:cloud` on the Ollama instance at 192.168.178.45:11434.
Several models on that instance are retired and fail at call time while
still appearing in the model list, so the default is one that was probed.

The system prompt tells the model never to call a reading impossible: a
gravity below 1.000 is always a mis-entry, but the rest of the run may be a
genuine long fermentation and still worth understanding.

150 tests.

src/flask/templates/active.html

@@ -100,6 +100,13 @@
         </div>
         {% endif %}
 
+        {% if run.advice %}
+        <div class="advice advice--reading{% if not run.advice_ok %} advice--failed{% endif %}">
+            <span class="advice__label">Brewing advice</span>
+            {{ run.advice }}
+        </div>
+        {% endif %}
+
         <div class="btn-row">
             <a class="btn btn--ghost btn--sm"
                href="{{ url_for('brews.run_detail', run_id=run.beer_run_id) }}">Open run</a>