feat: Implement Project Risk Scoring System (#273)

[SharifIbrahimDev]

Description

Implements a new ProjectRiskScorer class that aggregates individual findings from an analysis run into a single, project-level risk score. Closes #273.

What Changed

New Files

• src/analysis/scoring/project-risk-scorer.ts — Core scoring class
• src/analysis/scoring/project-risk-scorer.spec.ts — Full unit test coverage

Features

• Overall score normalized to 0–100 with letter grade (A–F) and risk level (low / medium / high / critical)
• Severity breakdown — counts per Critical / High / Medium / Low / Info
• Impact breakdown — counts across security, gas, performance, maintainability
• Total gas savings aggregated across all findings
• Top 5 findings ranked by score for immediate developer visibility
• Actionable recommendations auto-generated based on findings (e.g. critical security alerts, gas optimisation tips)
• Supports both raw Finding[] and standard AnalysisResult as input
• Configurable normalizationCeiling and ScoringConfig via constructor options

Testing

All new logic is covered by the unit tests in project-risk-scorer.spec.ts.

Closes #273