Add full-stack BTC portfolio web app

Multi-user FastAPI + React app with JWT auth, SQLite storage, and
CoinGecko price integration. Dockerized with docker-compose.

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

btc-portfolio/backend/app/auth.py

@@ -0,0 +1,28 @@
+from datetime import datetime, timedelta
+from jose import JWTError, jwt
+from passlib.context import CryptContext
+
+SECRET_KEY = "change-me-in-production-use-a-long-random-string"
+ALGORITHM = "HS256"
+ACCESS_TOKEN_EXPIRE_MINUTES = 60 * 24  # 1 day
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+
+def hash_password(password: str) -> str:
+    return pwd_context.hash(password)
+
+
+def verify_password(plain: str, hashed: str) -> bool:
+    return pwd_context.verify(plain, hashed)
+
+
+def create_access_token(data: dict) -> str:
+    to_encode = data.copy()
+    expire = datetime.utcnow() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
+    to_encode["exp"] = expire
+    return jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
+
+
+def decode_token(token: str) -> dict:
+    return jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])