Clear WatermelonDB and reset sync state when switching Synkronus servers

[Ndacyayisenga-droid]

When a user changes the Synkronus server URL in Formulus, the application does not reset local persistence or sync metadata. As a result, data and sync state from the previously configured server are reused against the newly selected server, leading to cross-server data corruption.

Root Cause

Although the API layer detects a server URL change and clears its internal configuration cache, local state is not cleared:

WatermelonDB retains all existing observation records.

Sync cursors (@last_seen_version, @last_attachment_version) stored in AsyncStorage remain unchanged.

This causes the client to treat the new server as a continuation of the old one.

Current Behavior

• Server URL is updated via settings.
• API config cache is reset.
• Local database contents and sync metadata persist unchanged.
• Next sync operation mixes old-server state with the new server.

Expected Behavior

On server URL change, the app should:

• Fully clear local observation data.
• Reset sync cursors to an initial state (e.g. version 0 or unset).
• Ensure no legacy app bundles or cached metadata interfere with the new server.
• Optionally notify the user that local data will be wiped.

Cc @r0ssing

[r0ssing]

Than you. This is a great analysis. I think we should consider the user warning and confirmation as necessary and not optional. Especially if there are unsynced records.

Attachments (photos etc) should also be cleared..