Add comprehensive test coverage for platform marketing homepage API:
- test_pricing.py: 17 tests for tiers, add-ons, pricing endpoints
- test_letzshop_vendors.py: 22 tests for vendor lookup and claiming
- test_signup.py: 28 tests for multi-step signup flow
Fix signup.py to use correct password hashing from middleware/auth.py
and properly create Company with owner_user_id.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
