feat: unify /me endpoint to aggregate all module profiles

GET /v1/iam/users/me now returns hackathon, QR, and mentor profiles
alongside the core IAM user data. Module-specific profiles are
included as optional fields when the user exists in those modules.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Cargo.lock

@@ -1970,6 +1970,7 @@ dependencies = [
  "sea-orm",
  "serde",
  "serde_json",
+ "sqlx",
  "strum 0.27.2",
  "strum_macros",
  "tokio",