feat: add n8n v2.0 external task runner support

upgrade n8n from 1.123.3 to 2.0.0-rc.4 with external task runners for
Code node execution. task runners handle javascript and python code
execution in isolated containers with configurable concurrency.

key changes:
- add n8n-runner service using n8nio/runners:2.0.0-rc.4
- configure runner auth token and broker communication
- add N8N_RUNNER_COUNT for scaling runner replicas
- move code node library config to runner container
- update binary data mode from filesystem to database
- add runner count prompt to installation wizard

.env.example

@@ -16,6 +16,7 @@ FLOWISE_PASSWORD=
 
 N8N_ENCRYPTION_KEY=
 N8N_USER_MANAGEMENT_JWT_SECRET=
+N8N_RUNNERS_AUTH_TOKEN=
 
 
 ############
@@ -171,9 +172,20 @@ WEBUI_HOSTNAME=webui.yourdomain.com
 
 RUN_N8N_IMPORT=
 
-# n8n worker configuration
+############
+# [optional]
+# n8n configuration
+############
+
 # Number of n8n worker replicas (for the n8n-worker service). Defaults to 1 if unset.
 N8N_WORKER_COUNT=
+
+# Number of n8n task runner replicas (for Code/Python node execution). Defaults to 1 if unset.
+N8N_RUNNER_COUNT=
+
+# Maximum number of concurrent Code node executions per task runner. Defaults to 5.
+N8N_RUNNERS_MAX_CONCURRENCY=5
+
 N8N_BLOCK_FILE_ACCESS_TO_N8N_FILES=true
 EXECUTIONS_MODE=queue
 N8N_LOG_LEVEL=info