Add per-item inventory sparklines with expandable history charts.

Co-authored-by: Cursor <cursoragent@cursor.com>

app.py

@@ -19,6 +19,7 @@ from db import (
     get_snapshot,
     import_save,
     init_db,
+    inventory_timeline,
     list_snapshots,
     get_connection,
     timeline,
@@ -113,6 +114,12 @@ def api_timeline(viewer_id: str):
     return jsonify(timeline(db_path=db_path))
 
 
+@viewer_bp.route("/api/inventory/timeline")
+def api_inventory_timeline(viewer_id: str):
+    db_path = _resolve_viewer_db(viewer_id)
+    return jsonify(inventory_timeline(db_path=db_path))
+
+
 @viewer_bp.route("/api/import", methods=["POST"])
 @limiter.limit(IMPORT_LIMIT)
 def api_import(viewer_id: str):