fix: addToInventory creates new row when all existing rows are opened

When adding a new pack of a product that already has an opened row
in inventory (opened_at IS NOT NULL), the previous code merged the
new stock into the opened row, corrupting opened_at tracking and
hiding the second pack from the anomaly model.

Now: search only for sealed rows (opened_at IS NULL) to merge into.
If only opened rows exist, INSERT a new sealed row instead.

CHANGELOG.md

@@ -11,6 +11,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - **Recipe scraps tips** — During cooking steps, detect "waste" generated (peels, cores, bones, eggshells, coffee grounds, citrus zest, etc.) and surface AI-powered tips on how to reuse them (compost, natural cleaner, broth, candied peel, etc.). Could be shown as an optional collapsible hint card below the step that generates the scrap.
 
+## [1.7.31] - 2026-05-29
+
+### Fixed
+- **New pack merges into opened pack on add** — `addToInventory` was looking for ANY existing row for the same product+location and adding the new quantity to it. This caused a newly purchased sealed pack to be silently merged with an already-opened pack, collapsing two physically distinct containers into one row and corrupting the `opened_at` timestamp. The fix now searches only for a **sealed** (unopened) row (`opened_at IS NULL`) to merge into. If only opened rows exist, a new sealed row is created instead — keeping the two packs separate and allowing the anomaly model and shelf-life tracker to work correctly.
+
+
 ## [1.7.30] - 2026-05-29
 
 ### Fixed