feat: grouped server cards with progress bars and sparklines

- Agent sends group name (defaults to hostname) and richer metric notes
  (memory/disk include absolute GB values; CPU note includes system uptime)
- push() accepts group param; server stores it as agent_group on deployments
- Upsert key is now (company_id, agent_group, name) so two agents on the
  same company but different servers don't overwrite each other's CPU/Memory
- Add widget config packs: linux-base, web-nginx, database-postgres/redis,
  docker-host, custom-cmd examples

ethica-agent.example.yml

@@ -4,9 +4,13 @@
 # Get it from: admin panel → Company → API tab → Company token
 #
 # token: REPLACE_ME          ← or set ETHICA_TOKEN in .env / environment
-# home: https://ethica.no   ← or set ETHICA_HOME  (default: https://ethica.no)
+# home: https://ethica.no   ← or set ETHICA_HOME   (default: https://ethica.no)
 # interval: 60               ← or set ETHICA_INTERVAL (seconds, default: 60)
+# group: my-server           ← or set ETHICA_GROUP  (default: system hostname)
+#                              All metrics from this agent are grouped under this
+#                              name in the Ethica dashboard (shows as a server card).
 
+group: my-server
 interval: 60
 
 widgets: