fix: refine Observe telemetry tables and themes

[Paulo Lacerda (placerda)]

Summary

• refine Observe tables with seconds, compact UTC timestamps, granular token columns, totals, and accessible metric help
• align model/deployment attribution and drill-through behavior across runtime and cost views
• share explicit URL-carried light/dark theming between Cockpit and Observe
• remove misleading unknown/not-reported labels from primary runtime tables

Validation

• python -m pytest tests/ -x -q (2463 passed, 1 skipped)
• Ruff on all changed Python files
• Playwright visual checks across Cockpit and every Observe tab