Migrate tooling to homelab; add OTel observability stack

- Remove GlitchTip, Umami, Fider, Gotify, Uptime Kuma, Dozzle, Watchtower
  from prod docker-compose (now run on homelab)
- Add dozzle-agent on prod (127.0.0.1:7007) for homelab Dozzle to connect to
- Remove corresponding subdomain blocks from Caddyfile (now routed via
  Cloudflare Tunnel from homelab)
- Add homelab/docker-compose.yml: unified homelab stack with all migrated
  tooling services plus full OTel stack (Tempo 2.6.1, Loki, Prometheus,
  OTel Collector, Grafana)
- Add homelab/otel/: Tempo, Loki, Prometheus, OTel Collector configs +
  Grafana provisioning (datasources + dashboards)
- Add homelab/dozzle/users.yml for Dozzle auth

homelab/otel/loki.yaml

@@ -0,0 +1,38 @@
+# Loki config — minimal single-node setup
+# Receives logs from OTel Collector. 30-day retention.
+
+auth_enabled: false
+
+server:
+  http_listen_port: 3100
+  grpc_listen_port: 9096
+
+common:
+  instance_addr: 127.0.0.1
+  path_prefix: /loki
+  storage:
+    filesystem:
+      chunks_directory: /loki/chunks
+      rules_directory: /loki/rules
+  replication_factor: 1
+  ring:
+    kvstore:
+      store: inmemory
+
+schema_config:
+  configs:
+    - from: 2024-01-01
+      store: tsdb
+      object_store: filesystem
+      schema: v13
+      index:
+        prefix: index_
+        period: 24h
+
+limits_config:
+  retention_period: 720h  # 30 days
+
+compactor:
+  working_directory: /loki/compactor
+  delete_request_store: filesystem
+  retention_enabled: true