feat: Add connection testing functionality for Rclone providers

- Introduced a new endpoint to test connections for source and destination providers.
- Implemented a TestResult component to display success or error messages based on connection outcomes.
- Enhanced the configuration form with buttons to initiate connection tests, improving user experience.
- Updated backend logic to handle connection testing and return appropriate feedback to the frontend.
- Refactored existing handlers and routes to accommodate the new testing functionality.

components/test_result.templ

@@ -0,0 +1,15 @@
+package components
+
+templ TestResult(success bool, message string) {
+	if success {
+		<div class="text-green-600 dark:text-green-400 flex items-center">
+			<i class="fas fa-check-circle mr-2"></i>
+			<span>{ message }</span>
+		</div>
+	} else {
+		<div class="text-red-600 dark:text-red-400 flex items-center">
+			<i class="fas fa-exclamation-triangle mr-2"></i>
+			<span>{ message }</span>
+		</div>
+	}
+}