fix: [BOUNTY] PII Export & Delete Workflow (GDPR-ready)

[pabloDarkmoon24]

Fixes #76

{
  "solution_code": "### FILE: app/routes/privacy.py\n\n```python\nimport io\nimport json\nimport zipfile\nimport logging\nfrom datetime import datetime, timezone\nfrom flask import Blueprint, jsonify, request, send_file, current_app, g\nfrom functools import wraps\n\nfrom app.db.connection import get_db\nfrom app.auth.middleware import jwt_required\nfrom app.audit import log_audit_event\n\nprivacy_bp = Blueprint('privacy', __name__, url_prefix='/users')\nlogger = logging.getLogger(__na