Add CORS support for frontend on localhost:3000

The frontend at http://localhost:3000 was getting CORS (Cross-Origin Resource Sharing)
errors when trying to make API requests to http://localhost:8000.

Added CORSMiddleware to FastAPI backend with:
- allow_origins: http://localhost:3000 and http://127.0.0.1:3000
- allow_credentials: true (for Authorization headers)
- allow_methods: all (GET, POST, OPTIONS, etc.)
- allow_headers: all (including Authorization, Content-Type, etc.)

This allows the browser to make cross-origin requests from the frontend to the API.

CORS headers now properly returned:
  access-control-allow-origin: http://localhost:3000
  access-control-allow-credentials: true

Co-authored-by: Copilot <[email protected]>

api/main.py

@@ -15,6 +15,7 @@ fundamental to scalable microservices architecture.
 
 from fastapi import FastAPI, Depends, HTTPException, status
 from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
+from fastapi.middleware.cors import CORSMiddleware
 from pydantic import BaseModel
 from jose import jwt, JWTError
 from kafka import KafkaProducer
@@ -129,6 +130,15 @@ app = FastAPI(
     version="1.0.0"
 )
 
+# Add CORS middleware to allow requests from frontend
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["http://localhost:3000", "http://127.0.0.1:3000"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
 @app.get("/health")
 async def health_check():
     """Health check endpoint"""