feat: improve header UI and optimize docker storage configuration

.env.example

@@ -4,6 +4,18 @@ APP_IMAGE=ghcr.io/your-org/projectx:sha-<git-sha>
 # App publish port on host
 APP_PORT=3000
 
+# Host folder that appears as /books in the container.
+# Point this at your library root; use an absolute path on NAS/Portainer installs.
+BOOKS_HOST_PATH=./books
+
+# Container runtime UID/GID for files written to app-managed data folders.
+# Most users can leave these defaults.
+PUID=1000
+PGID=1000
+
+# Node.js JavaScript heap limit in MB. Raise this for very large libraries.
+NODE_MAX_OLD_SPACE_SIZE=2048
+
 # Database credentials
 POSTGRES_USER=projectx
 POSTGRES_PASSWORD=change-this-password
@@ -28,6 +40,9 @@ APP_URL=https://projectx.example.com
 # CORS origin for the frontend when served from a different domain than APP_URL
 # CLIENT_URL=https://app.example.com
 
+# Set to false only if your platform manages bind mount ownership externally.
+# PROJECTX_FIX_PERMISSIONS=true
+
 # Recommended if you store SMTP provider credentials (generate: openssl rand -hex 32)
 # EMAIL_ENCRYPTION_KEY=