feat(aftersale): per-line refund/return flow with ledger-backed completion (add-aftersale-refunds)

apps/api/migrations/0016_aftersales.sql

@@ -0,0 +1,55 @@
+CREATE TYPE aftersale_kind AS ENUM ('refund_only', 'return_refund');
+
+CREATE TYPE aftersale_status AS ENUM (
+    'pending',
+    'approved',
+    'rejected',
+    'buyer_shipping',
+    'merchant_confirmed',
+    'refunded',
+    'cancelled'
+);
+
+-- Authoritative per-order refund total; every increment is a guarded UPDATE.
+ALTER TABLE orders
+    ADD COLUMN refund_total_minor BIGINT NOT NULL DEFAULT 0
+        CHECK (refund_total_minor >= 0);
+
+CREATE TABLE aftersales (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    order_id UUID NOT NULL REFERENCES orders (id),
+    order_item_id UUID NOT NULL REFERENCES order_items (id),
+    shop_id UUID NOT NULL REFERENCES shops (id),
+    user_id UUID NOT NULL REFERENCES users (id),
+    kind aftersale_kind NOT NULL,
+    status aftersale_status NOT NULL DEFAULT 'pending',
+    reason JSONB NOT NULL,
+    amount_minor BIGINT NOT NULL CHECK (amount_minor > 0),
+    evidence JSONB NOT NULL DEFAULT '[]',
+    reopened BOOLEAN NOT NULL DEFAULT false,
+    return_carrier TEXT,
+    return_tracking_no TEXT,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+-- At most one active (non-terminal) aftersale per order item.
+CREATE UNIQUE INDEX aftersales_one_active_per_item
+    ON aftersales (order_item_id)
+    WHERE status NOT IN ('refunded', 'rejected', 'cancelled');
+CREATE INDEX idx_aftersales_user ON aftersales (user_id);
+CREATE INDEX idx_aftersales_shop ON aftersales (shop_id);
+CREATE INDEX idx_aftersales_order ON aftersales (order_id);
+
+-- Append-only bilateral message log; no UPDATE/DELETE paths exist.
+CREATE TABLE aftersale_messages (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    aftersale_id UUID NOT NULL REFERENCES aftersales (id) ON DELETE CASCADE,
+    author_role TEXT NOT NULL CHECK (author_role IN ('buyer', 'merchant', 'platform')),
+    author_id UUID NOT NULL REFERENCES users (id),
+    content JSONB NOT NULL,
+    evidence JSONB NOT NULL DEFAULT '[]',
+    created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX idx_aftersale_messages_aftersale ON aftersale_messages (aftersale_id);