feat: improve networking, deployment, and roadmap

[pigeonligh]

Description

• Add a domain-aware SSH dialer manager with multiplexed connection pools, coordinated reconnects, adaptive expansion, keepalive handling, credential rotation, cleanup, and conformance coverage.
• Integrate the new SSH dialer manager with agent networking and limit the NodeServer timeout to connection establishment instead of the full connection lifetime.
• Initialize KCP management resources in deployment order and repair missing UI authentication secret fields without replacing valid values.
• Add English and Chinese project roadmaps and update the corresponding architecture and configuration documentation.

Motivation and Context

This change improves cross-cluster network reliability under concurrent load and transport failures, makes control-plane installation more robust for new and partially initialized environments, and documents RLark's planned extension model and platform direction.

How Has This Been Tested?

• Added unit tests for SSH pool lifecycle, concurrency, reconnect coordination, limits, keepalive behavior, cleanup, and credential changes.
• Added an SSH dialer conformance test program.
• Added a Kubernetes installer test for repairing incomplete UI authentication secrets.
• Full validation was not completed before opening this PR.