Document README quickstart network requirements

[Copilot]

The Getting Started flow did not call out the minimum networking needed for Flex Node traffic after join. This clarifies the baseline topology and points advanced setups to the lab docs.

• Quickstart requirements

  • Require peered/routed networks with non-overlapping CIDRs.
  • Require bidirectional private IP reachability between Flex hosts and AKS nodes.
  • Call out NSG/firewall allowance for node-to-node TCP/UDP traffic.

• Private and advanced topologies

  • Note private AKS DNS/API reachability requirements.
  • Direct advanced network scenarios such as cross-region, gateway, and custom CNI setups to the lab guides.

[Copilot]

Pull request overview

This PR updates the Getting Started quickstart in README.md to explicitly document baseline networking requirements for successfully joining and operating a Flex Node, and to route more complex/private topologies to the labs documentation.

Changes:

• Adds quickstart prerequisites around routed/peered networks, non-overlapping CIDRs, and bidirectional private IP reachability.
• Calls out NSG/firewall requirements for node-to-node (cross-node) traffic needed for pod networking post-join.
• Notes private AKS DNS/API endpoint reachability and points advanced scenarios to the lab guides.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.