Initial commit: CookIT recipe collection and week planner

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/adr/0003-units-are-data.md

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+# Units are data: built-in ones plus the cook's own
+
+Units used to be a fixed list in code. The cook wants to add their own (e.g. "Würfel"), choose which ones the picker offers directly and in what order, so units now live in a `units` table (schema version 2). The 27 built-in units are seeded from the `Unit` enum and keep their keys and localized names; the cook's own units get an `own-<uuid>` key and a stored name. Ingredient Lines keep storing just the unit's key, so existing recipes and version 1 Recipe Bundles stay valid.
+
+## Consequences
+
+- Recipe Bundles are version 2: they carry the cook's own units (`units`), and an import creates the ones that are missing. Version 1 bundles (the Excel converter's) still import.
+- Built-in units cannot be renamed or deleted: their keys are shared by every bundle and by the Excel converter.
+- Deleting an own unit rewrites the Ingredient Lines that used it ("2 Würfel Brühe": the name moves into the ingredient), so no recipe points at a unit that no longer exists.