Add feedback analytics and aggregation

[bchapuis]

Context

The feedback feature for workflow executions is already implemented:

• Database schema with feedback table (sentiment, comment, execution/workflow/deployment links)
• Full CRUD API at /:org/feedback/*
• Frontend components (ExecutionFeedbackCard, WorkflowFeedbackSection, FeedbackPage)

Goal

Add analytics and aggregation capabilities to allow users to assess workflows and deployments at a higher level.

Proposed Features

API

• Add endpoint to get aggregated feedback stats for a workflow (total count, positive %, negative %)
• Add endpoint to get aggregated feedback stats for a deployment
• Add filtering/date range support for analytics queries

Frontend

• Display feedback summary on workflow detail page (e.g., "85% positive from 20 ratings")
• Display feedback summary on deployment detail page
• Add charts/visualizations to the feedback dashboard page
• Show feedback trends over time

Related Files

• apps/api/src/routes/feedback.ts - API routes
• apps/api/src/db/schema/index.ts - Database schema (lines 424-457)
• apps/web/src/pages/feedback-page.tsx - Feedback dashboard
• packages/types/src/evaluation.ts - Type definitions