feat(DRW-001) initial commit!

migrations/20260911221511_create_items_table.up.sql

@@ -0,0 +1,14 @@
+CREATE TYPE item_source AS ENUM ('shop', 'neutral');
+
+CREATE TABLE items (
+    id SERIAL PRIMARY KEY,
+    name TEXT NOT NULL UNIQUE,
+    source item_source NOT NULL,
+    min_tier SMALLINT,
+    max_tier SMALLINT,
+    image_url TEXT NOT NULL,
+    CONSTRAINT neutral_tier_matches_source CHECK (
+        (source = 'neutral' AND min_tier BETWEEN 1 AND 5 AND max_tier BETWEEN 1 AND 5 AND min_tier <= max_tier)
+        OR (source = 'shop' AND min_tier IS NULL AND max_tier IS NULL)
+    )
+);