feat: Initial CBPOA commit — 武汉儿童呼吸疾病风险评估系统

Context: Build a spatial risk assessment system correlating air quality
data with children's respiratory disease incidence across Wuhan.

Approach: FastAPI backend serving PostGIS spatial queries, React
frontend with Deck.gl maps, and a PyTorch SpatialTemporalGCN pipeline
for multi-day (1d/3d/7d) risk prediction.

Changes:
- backend/ — FastAPI API with auth (JWT), alerts, risk analysis,
  geocoded case data, grid statistics, and report endpoints
- frontend/ — React dashboard with interactive risk maps, alert
  monitoring, district comparison charts, and timeline player
- models/ — SpatialTemporalGCN model with trained weights and ONNX
  export for inference
- scripts/ — ETL pipeline for weather + medical data, grid generation,
  feature engineering, training, and daily inference
- deploy/ — Docker Compose configs for backend, frontend, and MLflow
- docs/ — API docs, deployment guide, user guide, and code review

Impact: Enables spatial risk visualization, alert monitoring, and
ML-driven health risk forecasting for environmental health teams.

backend/auth/service.py

@@ -0,0 +1,66 @@
+"""JWT token creation and password hashing utilities."""
+import os
+import logging
+from datetime import datetime, timedelta, timezone
+
+from jose import JWTError, jwt
+from passlib.context import CryptContext
+
+logger = logging.getLogger("cbpoa.auth")
+
+SECRET_KEY = os.getenv("AUTH_SECRET_KEY", "cbpoa-dev-secret-change-in-production")
+ALGORITHM = "HS256"
+ACCESS_TOKEN_EXPIRE_MINUTES = int(os.getenv("AUTH_TOKEN_EXPIRE_MINUTES", "480"))
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+# In-memory user store (replace with DB table when auth matures)
+_users: dict[str, str] = {}
+
+
+def seed_default_admin() -> None:
+    """Create default admin user if no users exist."""
+    if not _users:
+        default_user = os.getenv("AUTH_DEFAULT_USER", "admin")
+        default_pass = os.getenv("AUTH_DEFAULT_PASSWORD", "admin123")
+        _users[default_user] = pwd_context.hash(default_pass)
+        logger.info("Seeded default user '%s'", default_user)
+
+
+def verify_password(plain: str, hashed: str) -> bool:
+    return pwd_context.verify(plain, hashed)
+
+
+def hash_password(password: str) -> str:
+    return pwd_context.hash(password)
+
+
+def authenticate_user(username: str, password: str) -> bool:
+    hashed = _users.get(username)
+    if not hashed:
+        return False
+    return verify_password(password, hashed)
+
+
+def create_user(username: str, password: str) -> bool:
+    """Register a new user. Returns False if username already exists."""
+    if username in _users:
+        return False
+    _users[username] = hash_password(password)
+    logger.info("Registered new user '%s'", username)
+    return True
+
+
+def create_access_token(data: dict) -> str:
+    to_encode = data.copy()
+    expire = datetime.now(timezone.utc) + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
+    to_encode.update({"exp": expire})
+    return jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
+
+
+def decode_access_token(token: str) -> dict | None:
+    try:
+        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
+        return payload
+    except JWTError:
+        return None