Feature: Idea Scoring

Description

As a product manager, I want to score backlog ideas based on impact, effort, and strategic fit so that the team can prioritize work objectively.

Requirements

• Create an Idea model with fields: title (string), impact (0-5), effort (0-5), strategic_fit (0-5)
• Create a score_idea function that computes: impact * 5 + strategic_fit * 3 - effort * 2
• Raise ValueError if any numeric field is outside the 0-5 range
• Keep the model immutable

Acceptance Criteria

1. An idea with impact=4, effort=2, strategic_fit=5 scores 31
2. An idea with impact=6 raises ValueError