fix: use hub.rat.dev mirror for base images

Buildkit ignores daemon.json registry-mirrors, so specify
mirror directly in FROM statements.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -1,5 +1,5 @@
 # Build stage - Python FastAPI application
-FROM python:3.12-slim AS build-stage
+FROM hub.rat.dev/library/python:3.12-slim AS build-stage
 
 WORKDIR /app
 
@@ -8,7 +8,7 @@ COPY requirements.txt ./
 RUN pip install --no-cache-dir -i https://mirrors.aliyun.com/pypi/simple/ -r requirements.txt
 
 # Production stage
-FROM python:3.12-slim AS production-stage
+FROM hub.rat.dev/library/python:3.12-slim AS production-stage
 
 WORKDIR /app
 

k8s-monitor/Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.12-slim
+FROM hub.rat.dev/library/python:3.12-slim
 
 WORKDIR /app
 

web/Dockerfile

@@ -1,5 +1,5 @@
 # Build stage
-FROM node:20-alpine AS build-stage
+FROM hub.rat.dev/library/node:20-alpine AS build-stage
 
 WORKDIR /app
 
@@ -16,7 +16,7 @@ ENV VITE_API_BASE_URL=$VITE_API_BASE_URL
 RUN npm run build
 
 # Production stage
-FROM nginx:stable-alpine AS production-stage
+FROM hub.rat.dev/library/nginx:stable-alpine AS production-stage
 
 COPY --from=build-stage /app/dist /usr/share/nginx/html