Replace hardcoded `users/` path-based access control with a
declarative `storageAccessPolicies` system defined per module via
`defineModule()`.
- Add `storageAccessPolicies` field to `defineModule()` defaults with
support for `owner` and `admin` policy types
- Expose `getAllStorageAccessPolicies()` from the modules/storage layer
- Refactor `handleGetFile` in `storage/api.js` to resolve access
control dynamically from registered policies instead of hardcoded
path checks
- Add `ZEN_STORAGE_ENDPOINT` env var and update `.env.example` to
support S3-compatible backends (Cloudflare R2, Backblaze B2)
- Document the env/doc sync convention in `DEV.md`
hykocx
2e348a1608