fix: auto-select remaining request after deleting second of two

[Fikri-20]

Fixes a bug where deleting the second request when only two exist leaves the UI with no request selected, even though one remains in the sidebar.

Video before resolving the bug

prob.mp4

Video after resolving the bug

sol.mp4

Root cause: lib/providers/collection_providers.dart line 131

// Before
} else if (itemIds.length > 1) {

// After
} else if (idx > 0) {

After removing the item, itemIds.length is 1 — so 1 > 1 is false and nothing gets selected. Using idx > 0 correctly selects the previous item regardless of list length.