Add script for TeslaMate battery capacity query

scripts/battery_capacity_by_mileage.py

@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+"""Query TeslaMate database for battery capacity by mileage.
+
+This script extracts the SQL used by the TeslaMate Grafana dashboard
+`battery-health.json` for the "Battery Capacity by Mileage" panel and
+executes it against a PostgreSQL database. The results are printed in
+a tab-separated format of odometer (km) and estimated capacity (kWh).
+"""
+
+import argparse
+import sys
+
+try:
+    import psycopg2
+except ImportError:  # pragma: no cover - require psycopg2
+    sys.exit("psycopg2 is required. Install with 'pip install psycopg2-binary'.")
+
+SQL = """
+SELECT
+    c.odometer,
+    c.charge_energy_added / (c.end_battery_level - c.start_battery_level) * 100
+        AS battery_capacity_kwh
+FROM charging_processes c
+WHERE c.car_id = %(car_id)s
+  AND c.charge_energy_added IS NOT NULL
+  AND (c.end_battery_level - c.start_battery_level) > 0
+ORDER BY c.odometer;
+"""
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Run TeslaMate 'Battery Capacity by Mileage' query."
+    )
+    parser.add_argument("--host", default="localhost", help="Database host")
+    parser.add_argument("--port", type=int, default=5432, help="Database port")
+    parser.add_argument("--user", default="teslamate", help="Database user")
+    parser.add_argument("--password", default="", help="Database password")
+    parser.add_argument("--database", default="teslamate", help="Database name")
+    parser.add_argument("--car-id", type=int, default=1, help="Car ID to query")
+    args = parser.parse_args()
+
+    conn_str = (
+        f"host={args.host} port={args.port} user={args.user} "
+        f"password={args.password} dbname={args.database}"
+    )
+
+    try:
+        with psycopg2.connect(conn_str) as conn:
+            with conn.cursor() as cur:
+                cur.execute(SQL, {"car_id": args.car_id})
+                for odometer, capacity in cur.fetchall():
+                    print(f"{odometer}\t{capacity:.2f}")
+    except Exception as exc:  # pragma: no cover - runtime path
+        print(f"Failed to run query: {exc}")
+        sys.exit(1)
+
+if __name__ == "__main__":
+    main()