feat: HTML/CSS ZIP preview upload for templates (extract + iframe)

feat: complete admin/client pages - orders, templates, projects, fields, versions, users, deployments

refactor: part 1 technical improvements - logging, response standards, caching, soft delete

refactor: major security, performance, and API quality improvements

fix: migrate old uploads to /data on startup for persistence across rebuilds

feat: persistent uploads dir, rebrand DesignFlow->Templyn, prefill admin login

Move rate limiter after static files, increase limit

Initial commit