feat(01-04): add onboarding wizard with settings API and persisted state

- Settings API: GET/PUT /api/settings/:key with SQLite persistence
- useSettings hook with TanStack Query for settings CRUD
- OnboardingWizard: 3-step modal overlay (welcome, create category, add item)
- Root layout checks onboarding completion flag before rendering wizard
- Skip option available at every step, all paths persist completion to DB

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

src/server/index.ts

@@ -5,6 +5,7 @@ import { itemRoutes } from "./routes/items.ts";
 import { categoryRoutes } from "./routes/categories.ts";
 import { totalRoutes } from "./routes/totals.ts";
 import { imageRoutes } from "./routes/images.ts";
+import { settingsRoutes } from "./routes/settings.ts";
 
 // Seed default data on startup
 seedDefaults();
@@ -21,6 +22,7 @@ app.route("/api/items", itemRoutes);
 app.route("/api/categories", categoryRoutes);
 app.route("/api/totals", totalRoutes);
 app.route("/api/images", imageRoutes);
+app.route("/api/settings", settingsRoutes);
 
 // Serve uploaded images
 app.use("/uploads/*", serveStatic({ root: "./" }));

src/server/routes/settings.ts

@@ -0,0 +1,37 @@
+import { Hono } from "hono";
+import { eq } from "drizzle-orm";
+import { db as prodDb } from "../../db/index.ts";
+import { settings } from "../../db/schema.ts";
+
+type Env = { Variables: { db?: any } };
+
+const app = new Hono<Env>();
+
+app.get("/:key", (c) => {
+  const database = c.get("db") ?? prodDb;
+  const key = c.req.param("key");
+  const row = database.select().from(settings).where(eq(settings.key, key)).get();
+  if (!row) return c.json({ error: "Setting not found" }, 404);
+  return c.json(row);
+});
+
+app.put("/:key", async (c) => {
+  const database = c.get("db") ?? prodDb;
+  const key = c.req.param("key");
+  const body = await c.req.json<{ value: string }>();
+
+  if (!body.value && body.value !== "") {
+    return c.json({ error: "value is required" }, 400);
+  }
+
+  database
+    .insert(settings)
+    .values({ key, value: body.value })
+    .onConflictDoUpdate({ target: settings.key, set: { value: body.value } })
+    .run();
+
+  const row = database.select().from(settings).where(eq(settings.key, key)).get();
+  return c.json(row);
+});
+
+export { app as settingsRoutes };