feat: integrated diagnostics dashboard and unified log aggregation

[zeroasterisk]

Problem

There is no unified logging aggregation. When an agent fails to start, the Hub UI doesn't display stdout/stderr. To figure out why an agent is stuck, the operator must SSH into the host, run docker logs scion-hub, and then find a way to attach to the inner agent's tmux logs.

This debugging friction exists across all deployment targets — the lack of integrated diagnostics is a platform gap, not an environment-specific issue.

Proposal

(f) Integrated Web Log Viewer

Build a centralized "Diagnostics & Logs" dashboard inside the Hub UI. This panel should:

• Stream live, aggregated logs from the Hub server, the runtime broker, and active agent container outputs
• Present in a single, color-coded stream
• Include built-in log level filters (INFO, WARN, ERROR)
• Support agent-level log isolation (view logs for a specific agent)

Auto-Healing and Verification Checks

The make doctor utility or the Hub startup script should verify that the active container image is fully in-sync with the current Dockerfile dependencies. If a binary (like docker) is missing from the container, it should raise a clear warning in the Hub UI:

"Hub image out-of-sync. Rebuild suggested: run 'make rebuild'."

This prevents silent failures where the hub appears running but can't actually manage containers because its own image is stale.

Related Issues

• Blank Web ui in workstation mode #174 — Blank web UI in workstation mode
• Admin settings saved via web UI are lost on pod restart in Kubernetes deployments #147 — Admin settings lost on pod restart (symptom of no config diagnostics)