[Good First Issue] Implement WebSocket real-time run status updates

[Oshgig]

Overview

The dashboard currently polls for run status. We need a WebSocket endpoint so the frontend can receive real-time push updates when a prediction job completes or fails.

Scope

• Implement /ws/runs/{run_id} WebSocket endpoint in FastAPI
• Emit status updates: running → completed / failed
• Include result payload (or error message) in the final completed/failed event
• Handle client disconnections gracefully
• Update frontend useRunPolling hook to prefer WebSocket, falling back to polling
• Update NewAnalysis and RunHistory pages to listen for WebSocket events

Acceptance Criteria

• Opening a WebSocket connection to /ws/runs/{run_id} receives status updates in real time
• Frontend replaces polling with WebSocket when supported
• Connection gracefully degrades to polling if WebSocket is unavailable
• All changes covered by at least basic tests

Resources

• src/climatevision/api/main.py — existing FastAPI app
• frontend/src/ — React dashboard
• team_docs/PM_ROLE_UPDATES_FOR_GAPS.md — gap [Good First Issue] Add frontend unit tests with Vitest + React Testing Library #9 details

Difficulty: Intermediate
Labels: help wanted, backend, frontend, real-time