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/logging_config.py

@@ -0,0 +1,59 @@
+"""
+Structured logging configuration for CBPOA backend.
+
+- LOG_LEVEL: DEBUG, INFO, WARNING, ERROR, CRITICAL (default INFO)
+- LOG_FORMAT: "json" for production, "text" for human-readable dev output (default text)
+"""
+import logging
+import json
+import sys
+import os
+from datetime import datetime, timezone
+
+
+class JSONFormatter(logging.Formatter):
+    """Emit structured JSON log lines for production."""
+
+    def format(self, record: logging.LogRecord) -> str:
+        log_entry = {
+            "timestamp": datetime.fromtimestamp(record.created, tz=timezone.utc).isoformat(),
+            "level": record.levelname,
+            "logger": record.name,
+            "message": record.getMessage(),
+        }
+        if record.exc_info and record.exc_info[1]:
+            log_entry["exception"] = self.formatException(record.exc_info)
+        # Include extra fields (request_id, method, path, etc.)
+        for key in ("request_id", "method", "path", "status_code", "duration_ms"):
+            val = getattr(record, key, None)
+            if val is not None:
+                log_entry[key] = val
+        return json.dumps(log_entry, ensure_ascii=False)
+
+
+def setup_logging() -> None:
+    """Configure root logger based on environment variables."""
+    level_name = os.getenv("LOG_LEVEL", "INFO").upper()
+    level = getattr(logging, level_name, logging.INFO)
+
+    log_format = os.getenv("LOG_FORMAT", "text").lower()
+
+    handler = logging.StreamHandler(sys.stdout)
+
+    if log_format == "json":
+        handler.setFormatter(JSONFormatter())
+    else:
+        handler.setFormatter(
+            logging.Formatter(
+                "%(asctime)s | %(levelname)-8s | %(name)s | %(message)s",
+                datefmt="%Y-%m-%d %H:%M:%S",
+            )
+        )
+
+    root = logging.getLogger()
+    root.handlers.clear()
+    root.addHandler(handler)
+    root.setLevel(level)
+
+    # Quiet noisy third-party loggers
+    logging.getLogger("uvicorn.access").setLevel(logging.WARNING)