Add real total node count

[louisevelayo]

Description: Node Monitor currently calculates node totals based on the public Internet Computer (IC) dashboard. This can lead to inaccuracies if a node is down for an extended period and temporarily removed from the network. As a result, Node Monitor may incorrectly show all systems as healthy when a node is actually down but unmonitored.

Proposed Solution:

• User Input: Allow users to specify the total number of nodes in their data center.
• Database Update: Add a field in the subscribers table to store this total node count.

Additional Considerations:

• Ensure that Node Monitor's logic is updated to compare the actual number of active nodes (based on user input) against those currently visible on the IC dashboard.
• Implement alerts or notifications when there is a mismatch between the total nodes expected and the nodes currently monitored.
• Consider how these changes might affect existing subscribers and ensure a smooth transition to the new system.

These changes will improve Node Monitor's accuracy by ensuring it reflects the actual state of nodes, even if some are temporarily removed from the IC dashboard.