Drag to reorder tracking categories (v0.22.0-beta.1)

[mapgie]

Summary

• Drag to reorder active categories — long-press the drag handle (≡) on any active tracking category to pick it up and drag it to a new position. Items animate smoothly as you drag. The new order is written to displayOrder on release and persists across app restarts.
• Works alongside existing swipe-to-archive (left) and swipe-to-delete (right) gestures — the long-press requirement prevents accidental activation during swipes.
• System categories (Flow, Symptoms) are also reorderable.
• Archived categories have no drag handle (reordering archived items makes no sense).

Implementation notes

• No DB migration needed — displayOrder: Int column already exists on TrackingCategory.
• SnapshotStateList (localActive) mirrors the ViewModel's active list locally. Drag swaps happen immediately in the local list for instant visual feedback; reorderCategories() is called on drag end to persist the order.
• detectDragGesturesAfterLongPress on the handle icon; items swap at the midpoint threshold using LazyListState.layoutInfo.visibleItemsInfo for item height.
• Modifier.animateItem() on each active row for smooth swap animation.

Test plan

• Long-press drag handle on a category and drag up/down — items should swap smoothly
• Release drag — order should persist after navigating away and back
• Swipe left/right on a category — archive/delete should still work normally
• App restart — reordered categories should appear in the new order
• Archived section still collapsible and unaffected by reorder

https://claude.ai/code/session_01AGmvoYfqqkLA9SUWV6myXW

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