docs(obs): update .env.example for PORT_GRAFANA 3003, POSTGRES_HOST, $$ escaping

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -29,16 +29,17 @@ OCR_TRAINING_TOKEN=change-me-in-production
 # --- Observability ---
 # Optional stack — start with: docker compose -f docker-compose.observability.yml up -d
 # Requires the main stack to already be running (docker compose up -d creates archiv-net).
+# In production the stack is managed from /opt/familienarchiv/ (see docs/DEPLOYMENT.md §4).
 
 # Ports for host access
-PORT_GRAFANA=3001
+PORT_GRAFANA=3003
 PORT_GLITCHTIP=3002
 PORT_PROMETHEUS=9090
 
 # Grafana admin password — change this before exposing Grafana beyond localhost
 GRAFANA_ADMIN_PASSWORD=changeme
 
-# GlitchTip domain — production: use https://grafana.raddatz.cloud (must match Caddy vhost)
+# GlitchTip domain — production: use https://glitchtip.archiv.raddatz.cloud (must match Caddy vhost)
 GLITCHTIP_DOMAIN=http://localhost:3002
 
 # GlitchTip secret key — Django SECRET_KEY equivalent, used to sign sessions and tokens.
@@ -47,6 +48,15 @@ GLITCHTIP_DOMAIN=http://localhost:3002
 # Generate with: python3 -c "import secrets; print(secrets.token_hex(50))"
 GLITCHTIP_SECRET_KEY=changeme-generate-a-real-secret
 
+# PostgreSQL hostname for GlitchTip's db-init job and workers.
+# Override when only the staging stack is running (container name differs from archive-db).
+# Default (archive-db) is correct for production with the full stack up.
+POSTGRES_HOST=archive-db
+
+# $$ escaping note: passwords in /opt/familienarchiv/.env that contain a literal '$' must
+# use '$$' so Docker Compose does not expand them as variable references.
+# Example: a password 'p@$$word' should be written as 'p@$$$$word' in the .env file.
+
 # Error reporting DSNs — leave empty to disable the SDK (safe default).
 # SENTRY_DSN: backend (Spring Boot) — used by the GlitchTip/Sentry Java SDK
 SENTRY_DSN=