feat: Enhance form validation and error handling

- Improve transaction form validation with detailed error messages
- Add proper type checking for amount and date inputs
- Enhance error handling in transactions API
- Improve code documentation and organization
- Convert TODO comments to proper documentation blocks

.astro/types.d.ts

@@ -1 +1,2 @@
 /// <reference types="astro/client" />
+/// <reference path="content.d.ts" />