anchor-based zoom levels, week separators in chart, UI polish

Program.cs

@@ -15,6 +15,14 @@ var app = builder.Build();
 app.UseDefaultFiles();
 app.UseStaticFiles();
 
+// GET /api/settings
+app.MapGet("/api/settings", (IConfiguration config) =>
+{
+    var anchorDay = int.TryParse(config["AnchorDay"], out var d) ? d : 4;  // 0=Sun, 4=Thu
+    var anchorHour = int.TryParse(config["AnchorHour"], out var h) ? h : 23;
+    return Results.Ok(new { anchorDay, anchorHour });
+});
+
 // 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) =>