dynamic bar count (multiples of 28), header overflow fix, parentId index for faster chain lookups

Program.cs

@@ -15,6 +15,14 @@ var app = builder.Build();
 app.UseDefaultFiles();
 app.UseStaticFiles();
 
+// Ensure indexes for chain lookups
+using (var db = app.Services.GetRequiredService<Func<SqliteConnection>>()())
+{
+    db.Open();
+    db.Execute("CREATE INDEX IF NOT EXISTS idx_entries_parentId ON entries(json_extract(data, '$.parentId'))");
+}
+
+
 // GET /api/cost-buckets?from=&to=&bucketMinutes=
 // Returns N buckets of aggregated cost
 app.MapGet("/api/cost-buckets", (Func<SqliteConnection> factory, string from, string to, int bucketMinutes) =>