Summary

Implements the GDPR PII Export & Delete workflow requested in #76:

• GET /gdpr/export — Collects all user-linked data (profile, categories, expenses, recurring expenses, bills, reminders, subscriptions) into a structured JSON download. Excludes password_hash. Logs a PII_EXPORT audit event.
• POST /gdpr/delete — Permanently deletes the user account after password re-verification. Uses the existing ON DELETE CASCADE foreign keys for clean removal. Writes an ACCOUNT_DELETED audit log entry that survives deletion via ON DELETE SET NULL.
• GET /gdpr/audit — Returns the user's audit trail sorted by most recent first.

Implementation Details

• Follows existing codebase patterns: Flask Blueprint, @jwt_required(), SQLAlchemy queries
• 3 files changed: new routes/gdpr.py, new tests/test_gdpr.py, updated routes/__init__.py
• No schema migrations needed — leverages existing FK cascade behavior
• Password re-verification required before deletion (uses check_password_hash)
• Audit logs persist after user deletion (user_id becomes NULL per existing schema)

Tests

18 tests covering:

• Auth guards (401 on unauthenticated requests)
• Export completeness (all 7 data tables included)
• Password hash exclusion from exports
• Audit log creation on export
• Password verification for deletion
• Wrong password rejection
• User removal confirmation
• Cascade deletion of expenses and categories
• Audit log preservation after user deletion
• Audit trail retrieval

Checklist

• Follows existing code style and patterns
• All endpoints require JWT authentication
• Password re-verification before irreversible deletion
• Audit trail survives account deletion
• Tests included for all acceptance criteria
• No new dependencies added

/claim #76

Closes #76