feat: app health endpoint succeeds (E00-S02-T03)

compose.yaml

@@ -1,4 +1,4 @@
-# EPPP Docker Compose baseline — [E00-S02-T01/T02]
+# EPPP Docker Compose baseline — [E00-S02-T01/T02/T03]
 #
 # `docker compose up -d` starts both the database (PostgreSQL) and the
 # application (@personal-blog/server). Rollback: `docker compose down`.
@@ -8,8 +8,11 @@
 # `condition: service_healthy`, so the application does not start until the
 # database is accepting connections.
 #
-# Explicitly out of scope for T01/T02 (land in later E00-S02 tasks):
-#   - application health endpoint (T03)
+# Application health endpoint (T03): the app serves `GET /health` (HTTP 200 +
+# `{"status":"ok"}`) on port 3000, so the app container stays up and the
+# health endpoint succeeds once the stack is running.
+#
+# Explicitly out of scope for T01/T02/T03 (land in later E00-S02 tasks):
 #   - DB volume persistence (T04)
 #
 # All values have defaults so `docker compose up -d` works from a clean clone