feat: add import/export flow for saved plans in the demo

[HyTaXx]

• Add IndexedDB helpers to export and import plans; surface Export/Import controls in example/src/views/HomeView.vue; strip existing ids when importing so new entries get fresh keys and refresh the list after import.

[pgiraud]

I quickly gave your proposal a try. I'm not reluctant to integrate it. However, can you please elaborate what the use case for this feature is? Which user needs does it fulfill? Can you detail one or more user scenario?

[HyTaXx]

Hi @pgiraud, ty for the feedback !

In our use case, we rely on the standalone app rather than always running in a hosted environment. Having Import / Export capabilities is valuable because :

• It supports working across different machines or browsers : for example a user can export their plans from one browser and quickly restore them on an other.
• It simplifies sharing as plans can easily be exported and transferred and then imported by a colleague or an other setup.

So the main benefit is making plans more portable and reducing friction when switching contexts or collaborating

[pgiraud]

Hello @HyTaXx,

I played with your proposed changes and decided to push a step further.
Can you please give a look at this new PR and tell me what you think?

[pgiraud]

#837 has been merged. @HyTaXx I kept you as co-author for this nice feature.