feat(06-02): create health check endpoint

- Returns 200 'ok' when database is accessible
- Returns 503 'unhealthy' when database query fails
- Simple text response for Docker HEALTHCHECK

src/routes/health/+server.ts

@@ -0,0 +1,22 @@
+import type { RequestHandler } from './$types';
+import { db } from '$lib/server/db';
+import { entries } from '$lib/server/db/schema';
+
+export const GET: RequestHandler = async () => {
+	try {
+		// Verify database connectivity with a simple query
+		db.select().from(entries).limit(1).all();
+
+		return new Response('ok', {
+			status: 200,
+			headers: { 'Content-Type': 'text/plain' }
+		});
+	} catch (error) {
+		console.error('Health check failed:', error);
+
+		return new Response('unhealthy', {
+			status: 503,
+			headers: { 'Content-Type': 'text/plain' }
+		});
+	}
+};