feat: complete inventory image and sales workflows

Commit the working vertical slices for inventory image processing and the Sale workflow, including Sale history, audited voiding, multi-item persistence, admin UI, migrations, documentation, and tests.

database/migrations/0012_sales.sql

@@ -0,0 +1,30 @@
+CREATE TABLE "sales" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"seller_id" uuid NOT NULL REFERENCES "sellers"("id"),
+	"sale_date" text NOT NULL,
+	"sale_location" text,
+	"sold_price_minor" integer NOT NULL,
+	"currency" text NOT NULL,
+	"platform_fees_minor" integer DEFAULT 0 NOT NULL,
+	"payment_processing_fees_minor" integer DEFAULT 0 NOT NULL,
+	"shipping_cost_minor" integer DEFAULT 0 NOT NULL,
+	"taxes_minor" integer DEFAULT 0 NOT NULL,
+	"other_fees_minor" integer DEFAULT 0 NOT NULL,
+	"buyer_name" text,
+	"buyer_contact" text,
+	"notes" text,
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	"updated_at" timestamp with time zone DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+CREATE TABLE "sale_items" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"sale_id" uuid NOT NULL REFERENCES "sales"("id"),
+	"inventory_item_id" uuid NOT NULL REFERENCES "inventory_items"("id"),
+	"sold_price_minor" integer NOT NULL,
+	"cost_basis_minor" integer NOT NULL
+);
+--> statement-breakpoint
+CREATE UNIQUE INDEX "sale_items_inventory_item_id_unique" ON "sale_items" USING btree ("inventory_item_id");
+--> statement-breakpoint
+CREATE INDEX "sale_items_sale_id_index" ON "sale_items" USING btree ("sale_id");