feat: add OEM code copy tracking, PostHog analytics, Postal email integration

- Add oem_code_copies table and analytics module for tracking part code copies
- Integrate PostHog for frontend product analytics (VIN decode, OEM copy events)
- Switch email service from stub to Postal API with proper error handling
- Add copy button to parts panel with clipboard + server-side logging
- Add admin copy-logs page with filtering and top-copied-codes view
- Add VIN report endpoint for users to flag unrecognized chassis numbers
- Add Postal email env vars to config schema

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/api/src/database/schema/core.ts

@@ -210,6 +210,27 @@ export const queryLogs = pgTable(
   ],
 );
 
+// ─── OEM Code Copies ──────────────────────────────────
+export const oemCodeCopies = pgTable(
+  "oem_code_copies",
+  {
+    id: uuid("id").primaryKey().defaultRandom(),
+    userId: uuid("user_id")
+      .notNull()
+      .references(() => users.id, { onDelete: "cascade" }),
+    oemCode: varchar("oem_code", { length: 100 }).notNull(),
+    partId: uuid("part_id"),
+    vehicleId: uuid("vehicle_id"),
+    categoryId: uuid("category_id"),
+    createdAt: timestamp("created_at", { withTimezone: true }).defaultNow().notNull(),
+  },
+  (table) => [
+    index("oem_code_copies_user_id_created_at_idx").on(table.userId, table.createdAt),
+    index("oem_code_copies_oem_code_idx").on(table.oemCode),
+    index("oem_code_copies_created_at_idx").on(table.createdAt),
+  ],
+);
+
 // ─── Vehicles ───────────────────────────────────────
 export const vehicles = pgTable(
   "vehicles",