admin: add Total imported and Last sync columns to Garmin sync table

Matches the Strava sync table layout. Accumulates total_imported in
garmin_sync.json state on each sync run; admin API exposes last_sync_at
and total_imported from that file.

bincio/serve/routers/admin.py

@@ -607,6 +607,17 @@ async def admin_garmin_sync_status(
         user_dir = cf.parent
         handle = user_dir.name
 
+        last_sync: str | None = None
+        total_imported = 0
+        sync_path = user_dir / "garmin_sync.json"
+        if sync_path.exists():
+            try:
+                sc = json.loads(sync_path.read_text(encoding="utf-8"))
+                last_sync = sc.get("last_sync_at")
+                total_imported = sc.get("total_imported", 0)
+            except (OSError, json.JSONDecodeError):
+                pass
+
         run_status: str | None = None
         run_imported = 0
         run_errors = 0
@@ -626,6 +637,8 @@ async def admin_garmin_sync_status(
 
         users.append({
             "handle": handle,
+            "last_sync": last_sync,
+            "total_imported": total_imported,
             "run_status": run_status,
             "run_imported": run_imported,
             "run_errors": run_errors,