[Refactor] Standardize Type Definitions for Contributor Profiles

[mijinummi]

Unified Contributor Types

Description
Contributor-related types are currently fragmented across the codebase. This task centralizes them into packages/types to establish a single source of truth.

Task

• Define a unified ContributorProfile interface
• Ensure all adapters (GitHub, Snapshot, Discord) conform to this interface

Goal
Improve type safety, consistency, and long-term maintainability across the monorepo.