Add consistent API request logging and a themed 404 page, bump to 0.4.0

Every app/api route handler now goes through withRouteLogging, which logs
a correlated reqId/method/path/status/duration for each request and turns
any uncaught error into a logged stack trace plus a clean JSON 500 instead
of Next's default opaque failure. proxy.ts logs rejected auth attempts, and
instrumentation.ts's onRequestError catches anything that still escapes a
route handler. Also adds a minimal not-found page matching the app's card
styling.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/api/play-sessions/route.ts

@@ -1,6 +1,7 @@
 import { NextResponse } from "next/server";
 import { z } from "zod";
 import { listPlaySessions, startPlaySession } from "@/lib/db/queries/play-sessions";
+import { withRouteLogging } from "@/lib/api/with-route-logging";
 
 const deviceInputSchema = z.object({
   slotLabel: z.string().min(1),
@@ -16,16 +17,16 @@ const bodySchema = z.object({
   devices: z.array(deviceInputSchema).min(1),
 });
 
-export async function GET() {
+export const GET = withRouteLogging("play-sessions.list", async () => {
   const rows = await listPlaySessions();
   return NextResponse.json({ playSessions: rows });
-}
+});
 
-export async function POST(req: Request) {
+export const POST = withRouteLogging("play-sessions.start", async (req: Request) => {
   const parsed = bodySchema.safeParse(await req.json().catch(() => null));
   if (!parsed.success) {
     return NextResponse.json({ error: parsed.error.message }, { status: 400 });
   }
   const result = await startPlaySession(parsed.data);
   return NextResponse.json(result, { status: 201 });
-}
+});