config modal: server-side settings (budget, anchor, bar width), removed localStorage

Program.cs

@@ -15,6 +15,27 @@ var app = builder.Build();
 app.UseDefaultFiles();
 app.UseStaticFiles();
 
+var configPath = Path.Combine(Path.GetDirectoryName(dbPath)!, "dashboard-config.json");
+
+// GET /api/config
+app.MapGet("/api/config", () =>
+{
+    if (File.Exists(configPath))
+        return Results.Text(File.ReadAllText(configPath), "application/json");
+    return Results.Text("{}", "application/json");
+});
+
+// PUT /api/config
+app.MapPut("/api/config", async (HttpRequest req) =>
+{
+    using var reader = new StreamReader(req.Body);
+    var json = await reader.ReadToEndAsync();
+    // Validate it's valid JSON
+    System.Text.Json.JsonDocument.Parse(json);
+    await File.WriteAllTextAsync(configPath, json);
+    return Results.Ok(new { ok = true });
+});
+
 // Ensure indexes for chain lookups
 using (var db = app.Services.GetRequiredService<Func<SqliteConnection>>()())
 {