feat: add pricing observation API

Add seller-owned pricing observation persistence, median market valuation calculation, admin routes, contracts, validation, migration, and focused tests.

database/migrations/0015_pricing.sql

@@ -0,0 +1,30 @@
+CREATE TABLE "pricing_observations" (
+  "id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+  "product_id" uuid NOT NULL REFERENCES "products"("id"),
+  "inventory_item_id" uuid NOT NULL REFERENCES "inventory_items"("id"),
+  "provider_id" text NOT NULL,
+  "price_minor" integer NOT NULL,
+  "currency" text NOT NULL,
+  "source_identifier" text NOT NULL,
+  "condition_id" uuid NOT NULL REFERENCES "conditions"("id"),
+  "source_url" text,
+  "quality_score" integer,
+  "is_outlier" boolean DEFAULT false NOT NULL,
+  "outlier_reason" text,
+  "observed_at" timestamp with time zone DEFAULT now() NOT NULL,
+  "created_at" timestamp with time zone DEFAULT now() NOT NULL,
+  "updated_at" timestamp with time zone DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+CREATE INDEX "pricing_observations_inventory_item_id_index" ON "pricing_observations" USING btree ("inventory_item_id");
+--> statement-breakpoint
+CREATE TABLE "market_valuations" (
+  "id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+  "inventory_item_id" uuid NOT NULL REFERENCES "inventory_items"("id"),
+  "value_minor" integer NOT NULL,
+  "currency" text NOT NULL,
+  "strategy" text NOT NULL,
+  "confidence" text NOT NULL,
+  "source_count" integer NOT NULL,
+  "calculated_at" timestamp with time zone DEFAULT now() NOT NULL
+);

database/migrations/meta/_journal.json

@@ -106,6 +106,13 @@
       "when": 1789804800000,
       "tag": "0014_acquisitions",
       "breakpoints": true
+    },
+    {
+      "idx": 15,
+      "version": "7",
+      "when": 1789891200000,
+      "tag": "0015_pricing",
+      "breakpoints": true
     }
   ]
 }