fix: lazy-load Prisma client to fix build-time URL parsing

- Make Prisma client initialization lazy via Proxy
- Defer database-pool import until runtime
- Add guard for empty DATABASE_URL
- Build now succeeds with Next.js 16.1.4

.opencode/opencode.jsonc

@@ -0,0 +1,9 @@
+{
+  "$schema": "https://opencode.ai/config.json",
+  "mcp": {
+    "next-devtools": {
+      "command": ["npx", "-y", "next-devtools-mcp@latest"],
+      "type": "local",
+    },
+  },
+}