Add sleep time backfill script for timezone bug fix

Re-pulls N days of Garmin history using fixed utcfromtimestamp extraction.
INSERT OR REPLACE overwrites bad sleep_start/sleep_end values. Supports
--dry-run to preview suspicious rows before pulling.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: a-deal

scripts/backfill_sleep_times.py

@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+"""Backfill sleep_start/sleep_end in wearable_daily.
+
+The Garmin timezone bug (fixed in 64d5843) stored sleep times 7 hours
+early due to double-converting local timestamps. This script re-pulls
+90 days of Garmin data using the fixed extraction code, which overwrites
+the bad values via INSERT OR REPLACE.
+
+Usage:
+    python3 scripts/backfill_sleep_times.py [--days N] [--user USER_ID] [--dry-run]
+"""
+
+import argparse
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Backfill sleep times from Garmin")
+    parser.add_argument("--days", type=int, default=90, help="Days of history to re-pull")
+    parser.add_argument("--user", default="andrew", help="User ID")
+    parser.add_argument("--dry-run", action="store_true", help="Show what would change without pulling")
+    args = parser.parse_args()
+
+    from engine.gateway.db import get_db, init_db
+    init_db()
+    db = get_db()
+
+    # Show current bad data
+    person_row = db.execute(
+        "SELECT id FROM person WHERE health_engine_user_id = ?", (args.user,)
+    ).fetchone()
+    if not person_row:
+        print(f"No person found for user_id={args.user}")
+        sys.exit(1)
+
+    person_id = person_row["id"]
+    rows = db.execute(
+        """SELECT date, sleep_start, sleep_end FROM wearable_daily
+           WHERE person_id = ? AND source = 'garmin' AND sleep_start IS NOT NULL
+           ORDER BY date DESC LIMIT ?""",
+        (person_id, args.days),
+    ).fetchall()
+
+    print(f"Current sleep times for {args.user} ({len(rows)} rows with sleep data):")
+    suspicious = 0
+    for r in rows:
+        start = r["sleep_start"]
+        # Sleep start between 06:00-18:00 is suspicious (should be evening)
+        h = int(start.split(":")[0]) if start else 0
+        flag = " <-- SUSPICIOUS" if 6 <= h <= 18 else ""
+        if flag:
+            suspicious += 1
+        print(f"  {r['date']}  start={start}  end={r['sleep_end']}{flag}")
+
+    print(f"\n{suspicious}/{len(rows)} rows look wrong (sleep_start during daytime)")
+
+    if args.dry_run:
+        print("\n--dry-run: skipping re-pull")
+        return
+
+    if suspicious == 0:
+        print("No suspicious rows found. Nothing to backfill.")
+        return
+
+    print(f"\nRe-pulling {args.days} days of Garmin history with fixed timezone code...")
+    from engine.integrations.garmin import GarminClient
+    from engine.gateway.token_store import TokenStore
+
+    ts = TokenStore()
+    if not ts.has_token("garmin", args.user):
+        print(f"No Garmin tokens for {args.user}")
+        sys.exit(1)
+
+    token_dir = str(ts.garmin_token_dir(args.user))
+    client = GarminClient(token_dir=token_dir, token_store=ts, user_id=args.user)
+    client.connect()
+    series = client.pull_daily_series(days=args.days, person_id=person_id)
+    ts.sync_garmin_tokens(args.user)
+
+    print(f"\nPulled {len(series)} days. Verifying fix...")
+
+    # Show updated data
+    rows_after = db.execute(
+        """SELECT date, sleep_start, sleep_end FROM wearable_daily
+           WHERE person_id = ? AND source = 'garmin' AND sleep_start IS NOT NULL
+           ORDER BY date DESC LIMIT 10""",
+        (person_id,),
+    ).fetchall()
+
+    fixed = 0
+    for r in rows_after:
+        start = r["sleep_start"]
+        h = int(start.split(":")[0]) if start else 0
+        status = "OK" if not (6 <= h <= 18) else "STILL BAD"
+        if status == "OK":
+            fixed += 1
+        print(f"  {r['date']}  start={start}  end={r['sleep_end']}  [{status}]")
+
+    print(f"\n{fixed}/{len(rows_after)} recent rows now have correct sleep times.")
+
+
+if __name__ == "__main__":
+    main()