P1: Add premium dashboard sidebar, customizable model cards, adaptive probing, and detailed error banner

[xodapi]

Solution

1. Adaptive Probing:
   • In proxy.js, track the last probe timestamp for each model.
   • If a model is rate-limited and
     eset_in_seconds > 600 (more than 10 minutes remaining), only probe it once every 30 minutes. Otherwise, probe it at the default PROBE_INTERVAL.
2. Detailed Error Banner:
   • Update metrics.js snapshot to include
     ecent_errors (last 10 unique failures).
   • In dashboard.js, display detailed error reasons (e.g. �ig-pickle: 429 Rate limit exceeded) inside the top health banner so it's clear why errors are happening.
3. Customizable Model Cards:
   • In dashboard.js, render model cards dynamically based on a user-selected list of models stored in localStorage (oc-observed-models).
   • If the list is empty, default to config primary models (including �ig-pickle and others).
4. Premium Sidebar UI:
   • Introduce a fixed sidebar navigation bar on the left with rounded glassmorphic styling.
   • Sidebar options: 📊 Dashboard, ⚙️ Settings (customizing model cards, viewing environment configuration), and 🕸️ Request Flow.
   • Move 'Recent requests' and 'API limits' sections higher up on the main dashboard for easier access.