better deploys

sql/initial_schema.sql

@@ -824,3 +824,13 @@ CREATE TABLE IF NOT EXISTS public.receipt_items (
 COMMENT ON TABLE public.receipt_items IS 'Stores individual line items extracted from a user receipt.';
 CREATE INDEX IF NOT EXISTS idx_receipt_items_receipt_id ON public.receipt_items(receipt_id);
 CREATE INDEX IF NOT EXISTS idx_receipt_items_master_item_id ON public.receipt_items(master_item_id);
+
+-- 54. Store schema metadata to detect changes during deployment.
+CREATE TABLE IF NOT EXISTS public.schema_info (
+    id INT PRIMARY KEY DEFAULT 1,
+    schema_hash TEXT NOT NULL,
+    deployed_at TIMESTAMPTZ DEFAULT now() NOT NULL,
+    CONSTRAINT single_row_check CHECK (id = 1)
+);
+COMMENT ON TABLE public.schema_info IS 'Stores metadata about the deployed schema, such as a hash of the schema file, to detect changes.';
+COMMENT ON COLUMN public.schema_info.schema_hash IS 'A SHA-256 hash of the master_schema_rollup.sql file at the time of deployment.';