feat(08-01): add Prometheus /metrics endpoint with prom-client

- Install prom-client library for Prometheus metrics
- Create src/lib/server/metrics.ts with default Node.js process metrics
- Add /metrics endpoint that returns Prometheus-format text
- Exposes CPU, memory, heap, event loop metrics

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -39,6 +39,7 @@
 		"better-sqlite3": "^12.6.2",
 		"drizzle-orm": "^0.45.1",
 		"nanoid": "^5.1.6",
+		"prom-client": "^15.1.3",
 		"sharp": "^0.34.5",
 		"svelecte": "^5.3.0",
 		"svelte-gestures": "^5.2.2",