feat: show read-only M0 research observations

[Pigbibi]

Summary

• add a default-collapsed M0 research observations section to the authenticated management console
• consume the read-only M0 dashboard endpoint with an unavailable-safe empty state
• show bounded research freshness, horizon context, conflicts, source digests, and viewed time only

Safety

• textContent-only rendering with a 100-observation display cap
• no buy/sell, weight, strategy, platform, switch, dispatch, runtime, or broker control is added
• M0 remains visibly research-only and no-order, separate from M1 Shadow

Validation

• node tests/strategy_switch_worker_validation.mjs passed locally
• diff check passed
• GitHub CI will run JS, Python, and workflow checks