[Remote rendering 4.2] Mode selection and remote entrypoint

### 📝 Description of the feature

Allow VISOR to start in either LOCAL (default) or REMOTE mode.

Backend entrypoint allowing selection of RenderingMode is already in place from 1.3 (wired to a remote stub). This builds the frontend equivalent for the first time.

On mount, the app opens a probe connection to the Trame server, reads which mode it's in and branches: for remote it keeps that connection open and hands it to the remote path rather than reopening one, for local it closes the probe and lets the local path take over. Remote mode must not initialize or download the wasm binary. Both modes serve from the same bundle.

### Acceptance Criteria

Remote mode downloads no wasm binary (no .wasm request in the network tab).
Tests pass

### 💵 Business Value

_No response_

### 🔗 Useful links and references

_No response_

Start at the app mount and the existing backend entrypoint for RenderingMode, then trace the Trame probe connection, remote handoff, and local wasm initialization. Run the project tests and verify that remote mode keeps the probe connection, while local mode closes it and remote mode makes no .wasm request.

Scritto dal modello di indicizzazione a partire dal testo della issue.