chore(deps): update node docker tag to v25

Dockerfile

@@ -1,4 +1,4 @@
-FROM node:20-alpine as build
+FROM node:25-alpine as build
 
 WORKDIR /app
 

backend/Dockerfile

@@ -1,4 +1,4 @@
-FROM node:20-slim
+FROM node:25-slim
 
 WORKDIR /app
 

renovate.json

@@ -0,0 +1,3 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json"
+}