Feature: Custom Dashboard Builder (Configurable Widgets & Layouts)

[hoangsonww]

Problem

Different users need different observability views (ops-focused, analytics-focused, debugging-focused). The current dashboard layout is fixed.

Proposal

Introduce a Custom Dashboard Builder where users can assemble widgets and save named layouts.

Scope

• Widget catalog (stat cards, active agents, event feed, heatmap, token chart, custom query tile)
• Drag-and-drop grid layout with resize handles
• Multiple saved layouts (e.g., "Incident", "Daily Monitoring")
• Per-layout refresh strategy and data source settings

UX Requirements

• One-click switch between saved layouts
• Reset to default layout
• Unsaved-change warning when editing layout

Technical Notes

• Persist user layout JSON in SQLite (dashboard_layouts)
• Use responsive grid that preserves desktop/mobile behavior
• Build widget interface contract (id, config schema, render, data requirements)

Acceptance Criteria

• User can create, rename, duplicate, and delete layouts
• User can add/remove/reorder widgets and resize them
• Layout state persists across restarts
• Default layout remains available as fallback
• Existing dashboard data APIs can back widgets without regressions