feat: add onboarding functionality and theme switch button

lib/screens/mobile/widgets/onboarding_slide.dart

@@ -0,0 +1,70 @@
+import 'package:apidash_design_system/apidash_design_system.dart';
+import 'package:flutter/material.dart';
+import 'package:lottie/lottie.dart';
+
+class OnboardingSlide extends StatelessWidget {
+  final BuildContext context;
+  final String assetPath;
+  final double assetSize;
+  final String title;
+  final String description;
+
+  const OnboardingSlide({
+    required this.context,
+    required this.assetPath,
+    required this.assetSize,
+    required this.title,
+    required this.description,
+    super.key,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      mainAxisAlignment: MainAxisAlignment.spaceBetween,
+      crossAxisAlignment: CrossAxisAlignment.center,
+      children: [
+        Padding(
+          padding: const EdgeInsets.only(top: 75.0),
+          child: Center(
+            child: Lottie.asset(
+              assetPath,
+              renderCache: RenderCache.drawingCommands,
+              width: assetSize,
+              fit: BoxFit.cover,
+            ),
+          ),
+        ),
+        Column(
+          mainAxisAlignment: MainAxisAlignment.start,
+          children: [
+            Text(
+              title,
+              textAlign: TextAlign.center,
+              style: TextStyle(
+                fontSize: 28,
+                fontWeight: FontWeight.bold,
+                color: Theme.of(context).colorScheme.primary,
+              ),
+            ),
+            const SizedBox(height: 10),
+            Padding(
+              padding: const EdgeInsets.symmetric(
+                vertical: 8.0,
+                horizontal: 16,
+              ),
+              child: Text(
+                description,
+                textAlign: TextAlign.center,
+                style: kTextStyleButton.copyWith(fontSize: 16),
+              ),
+            ),
+            const SizedBox(
+              height: 70,
+            )
+          ],
+        ),
+      ],
+    );
+  }
+}