fix: enforce gallery access and consolidate gallery workflows (#1357)

Harden gallery authentication and authorization, consolidate gallery workflows, and prevent token-bearing URLs from leaking through nginx request error logs.

.env.example

@@ -125,6 +125,11 @@ DB_NAME=picpeak_prod
 # address is refused by the SSRF check otherwise. Running n8n beside PicPeak is
 # normal, so set EMAIL_WEBHOOK_ALLOW_PRIVATE_URLS=true for that.
 #
+# Webhook and email-webhook deliveries connect to the DNS answer they just
+# validated and ignore HTTP_PROXY / HTTPS_PROXY. Behind a mandatory egress
+# proxy set the *_ALLOW_PRIVATE_URLS flag, which sends through the proxy
+# without pinning.
+#
 # A mail account with its own SMTP host (Settings -> Mail accounts) keeps
 # sending through it; this replaces the global transport only.
 #
@@ -353,3 +358,9 @@ LOGS=./logs
 # Backend signing-key encryption (32+ characters); defaults to JWT_SECRET.
 # Keep this value stable until participation has been deleted.
 # USAGE_ENCRYPTION_KEY=
+
+# Graceful shutdown budget in milliseconds. On SIGTERM the server stops
+# accepting requests, drains workers and closes the pool; whatever is still
+# running after this long is abandoned so the process exits before Docker's
+# 10 s stop grace period (raise stop_grace_period together with this value).
+#SHUTDOWN_TIMEOUT_MS=8000