Fix production deployment: replace serve with nginx reverse proxy

Frontend container now uses nginx to serve static files and proxy
/api/* requests to the backend container internally, eliminating
the hardcoded localhost:8000 build-time URL that caused "Network
error" on any non-local server. CORS origins are also configurable
via ALLOWED_ORIGINS env var.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

btc-portfolio/backend/app/main.py

@@ -1,3 +1,5 @@
+import os
+
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from sqlalchemy import text
@@ -9,9 +11,15 @@ Base.metadata.create_all(bind=engine)
 
 app = FastAPI(title="BTC Portfolio API")
 
+_raw_origins = os.environ.get(
+    "ALLOWED_ORIGINS",
+    "http://localhost:3000,http://localhost:3001",
+)
+allowed_origins = [o.strip() for o in _raw_origins.split(",") if o.strip()]
+
 app.add_middleware(
     CORSMiddleware,
-    allow_origins=["http://localhost:3000", "http://localhost:3001"],
+    allow_origins=allowed_origins,
     allow_credentials=True,
     allow_methods=["GET", "POST", "PUT", "DELETE", "OPTIONS"],
     allow_headers=["Content-Type", "Authorization"],

btc-portfolio/docker-compose.yml

@@ -8,6 +8,7 @@ services:
     environment:
       - DATABASE_URL=sqlite:////app/data/btc_portfolio.db
       - SECRET_KEY=${SECRET_KEY:-dev-insecure-key-change-me}
+      - ALLOWED_ORIGINS=${ALLOWED_ORIGINS:-http://localhost:3000,http://localhost:3001}
     restart: unless-stopped
     healthcheck:
       test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8000/')"]
@@ -20,14 +21,14 @@ services:
     build:
       context: ./frontend
       args:
-        - REACT_APP_API_URL=http://localhost:8000
+        - REACT_APP_API_URL=/api
     ports:
-      - "3001:3001"
+      - "3001:80"
     depends_on:
       - backend
     restart: unless-stopped
     healthcheck:
-      test: ["CMD", "wget", "-qO-", "http://localhost:3001/"]
+      test: ["CMD", "wget", "-qO-", "http://localhost:80/"]
       interval: 30s
       timeout: 10s
       retries: 3

btc-portfolio/frontend/Dockerfile

@@ -4,16 +4,12 @@ WORKDIR /app
 COPY package.json ./
 RUN npm install
 COPY . .
-ARG REACT_APP_API_URL=http://localhost:8000
+ARG REACT_APP_API_URL=/api
 ENV REACT_APP_API_URL=$REACT_APP_API_URL
 RUN npm run build
 
-FROM node:18-alpine
-RUN npm install -g serve
-RUN addgroup -S appgroup && adduser -S appuser -G appgroup
-WORKDIR /app
-COPY --from=build /app/build ./build
-RUN chown -R appuser:appgroup /app
-USER appuser
-EXPOSE 3001
-CMD ["serve", "-s", "build", "-l", "3001"]
+FROM nginx:alpine
+COPY --from=build /app/build /usr/share/nginx/html
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+EXPOSE 80
+CMD ["nginx", "-g", "daemon off;"]

btc-portfolio/frontend/nginx.conf

@@ -0,0 +1,20 @@
+server {
+    listen 80;
+    server_name _;
+
+    root /usr/share/nginx/html;
+    index index.html;
+
+    location /api/ {
+        proxy_pass         http://backend:8000/;
+        proxy_http_version 1.1;
+        proxy_set_header   Host              $host;
+        proxy_set_header   X-Real-IP         $remote_addr;
+        proxy_set_header   X-Forwarded-For   $proxy_add_x_forwarded_for;
+        proxy_set_header   X-Forwarded-Proto $scheme;
+    }
+
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+}