[Feature] Add persistence for original image during reloads

[chetanbarakki]

Is your feature request related to a problem?
Yes. At the moment, only the Blockly workspace is persisted in local storage. The imported source image is not saved, so after a page reload users have to upload the same image again before they can continue working. This breaks workflow continuity and makes the persisted workspace less useful, especially for longer sessions or when revisiting a saved pipeline later.

Describe the solution you'd like
Persist the currently loaded input image in local storage alongside the Blockly workspace state, and automatically restore it on reload. This should include: the original image data, the image format, the filename or display label

On app startup, the persisted image should be restored into the pipeline store and the Read Image block label should reflect the restored file name, so the editor returns to the same usable state as before reload. The persistence should be best-effort, with validation, expiry handling, and cleanup for invalid or oversized payloads.

Describe alternatives you've considered
A few alternatives were considered:

• Leaving image persistence out and continuing to persist only the Blockly workspace, but that still forces users to re-import images after every reload.
• Persisting processed images as well, but that adds extra storage cost and complexity while the main need is restoring the original input image.
• Using IndexedDB instead of local storage, which would better support larger images, but local storage is simpler and aligns with the current lightweight persistence approach for the workspace.