feat: add networkBridge to node model

[runleveldev]

This pull request adds support for configuring the Proxmox network bridge (networkBridge) used when creating containers. The change introduces a new networkBridge field to the Node model, database schema, and associated forms and routes, defaulting to 'vmbr0'. This allows users to specify which Proxmox bridge should be used per node, providing greater flexibility and clarity.

Database and Model Updates:

• Added a new non-nullable networkBridge column (default: 'vmbr0') to the Nodes table via a Sequelize migration.
• Updated the Node model to include the networkBridge attribute with the appropriate type and default value.

API and Form Handling:

• Updated the node creation (POST /), import (POST /import), and update (PUT /:id) routes to accept and handle the networkBridge field, defaulting to 'vmbr0' if not provided. [1] [2] [3] [4] [5]
• Added a new input field for networkBridge to the node form UI, pre-filled with the current value or 'vmbr0' by default.

Documentation:

• Updated the database schema diagram and documentation to reflect the new networkBridge field and its default value. [1] [2]