feat: Add Grafana auto-update & improve classifier

Add auto-update for Grafana on Synology via SSH + docker compose,
with review examples and a context.txt describing the specific setup
(Prometheus + Node Exporter, no plugins) so the classifier can
ignore plugin-only breaking changes.

The classifier now loads an optional context.txt per service to
tailor decisions to the actual deployment. It also truncates large
release notes intelligently, keeping important sections (breaking
changes, deprecations, migration notes) while dropping long PR
lists that add no signal.

test_classifier.py now also loads context.txt and accepts any
service name as argument.

services/grafana/review-examples/manual-1.txt

@@ -0,0 +1,17 @@
+action: manual
+reason: Major version bump that removes the viewers_can_edit setting and changes anonymous auth enforcement. These configuration changes could affect dashboard access. Admin should review config before upgrading.
+---
+[Download page](https://grafana.com/grafana/download/12.0.0)
+[What's new highlights](https://grafana.com/docs/grafana/latest/whatsnew/)
+
+### Breaking changes
+
+- **Alerting:** Make $value return the query value in case when a single datasource is used
+- **Anonymous:** Enforce org role Viewer setting
+- **Config:** Removes setting `viewers_can_edit`
+- **Frontend:** Remove Angular (Enterprise)
+- **Chore:** Enabling failWrongDSUID by default in Grafana 12
+
+### Deprecations
+
+- **Alerting:** Deprecate OpsGenie integration