Introduce Stage 4 features to support multi-user accounts, cookie-based web sessions, and personal dashboards.
Changes include:
- Adding `/register` to bootstrap the first admin account and `/login`/`/logout` for session management.
- Creating a personal dashboard (`/app`) to display owned boxes, storage usage, and upload history.
- Implementing admin user management (`/admin/users`) for generating invite links and managing user states.
- Updating the bbolt database schema to store users, sessions, invites, and collections.
- Adding `golang.org/x/crypto` for password hashing and introducing unit tests for account handlers.
Introduce an `AdminViewBox` handler and route that allows administrators
to view any box directly. If the box is password-protected, the handler
bypasses the protection by setting an unlock cookie with an unlock token
and logs the bypass event.
Additionally, add CSS and JS foundations for a file context menu and
preview actions in the file browser UI.
- Implement a token-authenticated admin console at `/admin` with overview metrics and file management.
- Add a background worker to periodically clean up expired boxes based on `WARPBOX_CLEANUP_EVERY`.
- Add a background worker to generate image and video thumbnails based on `WARPBOX_THUMBNAIL_EVERY`.
- Update file storage paths to use `@each@` and `@thumb@` prefixes to separate original files from thumbnails.
- Add severity fields to startup logs and update configuration templates.
