feat(01-02): implement item, category, and totals service layers

- Item CRUD: getAllItems with category join, getById, create, update, delete
- Category CRUD: getAll ordered by name, create, update, delete with reassignment
- Totals: per-category aggregates and global totals via SQL SUM/COUNT
- All 20 service tests passing

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server/services/totals.service.ts

@@ -0,0 +1,32 @@
+import { eq, sql } from "drizzle-orm";
+import { items, categories } from "../../db/schema.ts";
+import { db as prodDb } from "../../db/index.ts";
+
+type Db = typeof prodDb;
+
+export function getCategoryTotals(db: Db = prodDb) {
+  return db
+    .select({
+      categoryId: items.categoryId,
+      categoryName: categories.name,
+      categoryEmoji: categories.emoji,
+      totalWeight: sql<number>`COALESCE(SUM(${items.weightGrams}), 0)`,
+      totalCost: sql<number>`COALESCE(SUM(${items.priceCents}), 0)`,
+      itemCount: sql<number>`COUNT(*)`,
+    })
+    .from(items)
+    .innerJoin(categories, eq(items.categoryId, categories.id))
+    .groupBy(items.categoryId)
+    .all();
+}
+
+export function getGlobalTotals(db: Db = prodDb) {
+  return db
+    .select({
+      totalWeight: sql<number>`COALESCE(SUM(${items.weightGrams}), 0)`,
+      totalCost: sql<number>`COALESCE(SUM(${items.priceCents}), 0)`,
+      itemCount: sql<number>`COUNT(*)`,
+    })
+    .from(items)
+    .get();
+}