Add zoom in/out controls to Studio Canvas for improved navigation

### Feature Request: Incremental Zoom Controls in Frappe Studio Canvas

Currently, Frappe Studio's canvas only displays the current zoom level and has a reset (fit-to-screen) button. However, there's no easy way for users to zoom in or out incrementally.

This feature request proposes adding:

- A `+` button to zoom in
- A `−` button to zoom out
- Keep the existing **Fit to Screen** button

The issue targets the Frappe Studio Canvas and its existing zoom-level and Fit to Screen controls; start by locating the Canvas UI entry point and the current fit-to-screen control. Done means incremental + and − controls are available for zooming while the existing Fit to Screen button remains available.

Written by the indexing model from the issue text.