Handle server sync conflicts with explicit resolution actions

[avinxshKD]

Stop silent sync failures when local/remote history diverges.
On conflict, show one modal with clear choices: pull remote, force push local, open remote in new tab, or cancel.
Also surfaces local/remote hash context so the decision is informed.

closes #384

[avinxshKD]

Hey @pradeeban pls take a look, sync conflicts are now visible with clear recovery options instead of failing silently.

[avinxshKD]

Also, I’d like to work on a full sync-state layer with a dedicated status panel (local/remote hash, last sync result, and one-click resolve actions), so conflict handling is explicit and reliable end-to-end instead of message-dependent. What do you think?