Add historical data import functionality

- Add import_historical_data() method to EnhancedWaterMonitorScraper
- Support date range imports with Buddhist calendar API format
- Add CLI arguments --import-historical and --force-overwrite
- Include API rate limiting and skip existing data option
- Enable importing years of historical water level data

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/water_scraper_v3.py

@@ -576,6 +576,58 @@ class EnhancedWaterMonitorScraper:
             logger.debug(f"Error checking data existence: {e}")
             return False
 
+    def import_historical_data(self, start_date: datetime.datetime, end_date: datetime.datetime,
+                             skip_existing: bool = True) -> int:
+        """
+        Import historical data for a date range
+
+        Args:
+            start_date: Start date for historical import
+            end_date: End date for historical import
+            skip_existing: Skip dates that already have data (default: True)
+
+        Returns:
+            Number of data points imported
+        """
+        logger.info(f"Starting historical data import from {start_date.date()} to {end_date.date()}")
+
+        total_imported = 0
+        current_date = start_date
+
+        while current_date <= end_date:
+            try:
+                # Check if data already exists for this date
+                if skip_existing and self._check_data_exists_for_date(current_date):
+                    logger.info(f"Data already exists for {current_date.date()}, skipping...")
+                    current_date += datetime.timedelta(days=1)
+                    continue
+
+                logger.info(f"Importing data for {current_date.date()}...")
+
+                # Fetch data for this date
+                data = self.fetch_water_data_for_date(current_date)
+
+                if data:
+                    # Save to database
+                    if self.save_to_database(data):
+                        total_imported += len(data)
+                        logger.info(f"Successfully imported {len(data)} data points for {current_date.date()}")
+                    else:
+                        logger.warning(f"Failed to save data for {current_date.date()}")
+                else:
+                    logger.warning(f"No data available for {current_date.date()}")
+
+                # Add small delay to be respectful to the API
+                time.sleep(1)
+
+            except Exception as e:
+                logger.error(f"Error importing data for {current_date.date()}: {e}")
+
+            current_date += datetime.timedelta(days=1)
+
+        logger.info(f"Historical import completed. Total data points imported: {total_imported}")
+        return total_imported
+
 # Main execution for standalone usage
 if __name__ == "__main__":
     import argparse