devops(ci): add --wait to observability stack startup

Prometheus, Loki, Tempo, and Grafana all define healthchecks in
docker-compose.observability.yml. Without --wait, the step exits 0
as soon as containers are created, masking startup failures silently.

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

.gitea/workflows/nightly.yml

@@ -132,7 +132,7 @@ jobs:
           docker compose \
             -f docker-compose.observability.yml \
             --env-file .env.staging \
-            up -d
+            up -d --wait
 
       - name: Reload Caddy
         # Apply any committed Caddyfile changes before smoke-testing the

.gitea/workflows/release.yml

@@ -105,7 +105,7 @@ jobs:
           docker compose \
             -f docker-compose.observability.yml \
             --env-file .env.production \
-            up -d
+            up -d --wait
 
       - name: Reload Caddy
         # See nightly.yml — same rationale and mechanism: DooD job containers