feat: Implement major features and fix theming bug

This commit introduces several new features and a critical bug fix.

- Implemented a full "Quick Pay" flow for both within and outside the bank, including IFSC validation, beneficiary verification, and a TPIN-based payment process.
- Added a date range filter to the Account Statement screen and streamlined the UI by removing the amount filters.
- Fixed a major bug that prevented dynamic theme changes from being applied. The app now correctly switches between color themes.
- Refactored and improved beneficiary management, transaction models, and the fund transfer flow to support NEFT/RTGS.

lib/data/models/rtgs_response.dart

@@ -0,0 +1,16 @@
+class RtgsResponse {
+  final String message;
+  final String utr;
+
+  RtgsResponse({
+    required this.message,
+    required this.utr,
+  });
+
+  factory RtgsResponse.fromJson(Map<String, dynamic> json) {
+    return RtgsResponse(
+      message: json['message'] ?? '',
+      utr: json['utr'] ?? '',
+    );
+  }
+}