docs(showcase): add Perplexity Dart & Flutter SDKs showcase

docs/showcase/perplexity-flutter.mdx

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+---
+title: Perplexity Dart & Flutter SDKs
+description: Lightweight, type-safe SDKs for seamless Perplexity API integration in Dart and Flutter applications
+sidebar_position: 3
+keywords: [Perplexity, Flutter, Dart, SDK, API, streaming, chat-completions, sonar, type-safe, widgets]
+---
+
+# Perplexity Dart & Flutter SDKs
+
+**Perplexity Dart & Flutter SDKs** provide comprehensive toolkit for integrating Perplexity's AI capabilities into Dart and Flutter applications. Built specifically for the Flutter community, these packages include a lightweight core API client and ready-to-use Flutter widgets with BLoC state management.
+
+## Features
+
+* Type-safe API client with fully typed models and compile-time safety
+* Streaming and non-streaming chat completions with real-time response handling
+* Support for all Perplexity models (Sonar, Sonar Pro, Deep Research, Reasoning variants)
+* Multi-image processing with base64, data URI, and HTTPS URL support
+* Ready-to-use Flutter widgets with BLoC state management integration
+* Advanced configuration options (temperature, top-p, search filters, domain restrictions)
+* Cross-platform support for iOS, Android, Web, and Desktop
+* Future-proof design with custom model string support for new Perplexity releases
+
+## Prerequisites
+
+* Dart SDK 2.17.0 or newer
+* Flutter SDK 3.0.0 or newer (for Flutter-specific features)
+* Perplexity API key from Perplexity API Console
+* Basic knowledge of Flutter BLoC pattern for widget integration
+
+## Installation
+
+### For Dart Projects (Core API Only)
+
+```bash
+dart pub add perplexity_dart
+```
+
+### For Flutter Projects (Full Widget Support)
+
+```bash
+flutter pub add perplexity_flutter
+```
+
+### Environment variables
+
+```dart
+// Add to your app's configuration
+const String perplexityApiKey = 'your_perplexity_api_key_here';
+```
+
+## Usage
+
+**Core API Integration:**
+- Type-safe client with all Perplexity models (Sonar, Sonar Pro, Deep Research, Reasoning)
+- Streaming and non-streaming chat completions
+- Multimodal processing with flexible MessagePart system for text + images
+
+**Flutter Widget Layer:**
+- `ChatWrapperWidget` for BLoC state management 
+- `PerplexityChatView` for real-time message display
+- `PerplexityChatInput` for user interaction handling
+
+## Code Explanation
+
+* Core Layer: Pure Dart API client (`perplexity_dart`) for cross-platform Perplexity API integration
+* UI Layer: Flutter widgets (`perplexity_flutter`) with BLoC state management for rapid development
+* Type Safety: Fully typed models and responses prevent runtime errors and provide IntelliSense
+* Multimodal: Flexible MessagePart system for combining text and images in single requests
+* Streaming: Built-in support for real-time chat completions with proper chunk handling
+* Architecture: Two-layer design allows lightweight API usage or full Flutter widget integration
+
+## Architecture
+
+**Two-layer design:**
+- **Core (`perplexity_dart`)** - Pure Dart API client for all platforms
+- **UI (`perplexity_flutter`)** - Flutter widgets + BLoC state management
+
+Uses flexible MessagePart system for multimodal content combining text and images.
+## Links
+
+**Packages:**
+- [perplexity_dart on pub.dev](https://pub.dev/packages/perplexity_dart) | [GitHub](https://github.com/vishnu32510/perplexity_dart)
+- [perplexity_flutter on pub.dev](https://pub.dev/packages/perplexity_flutter) | [GitHub](https://github.com/vishnu32510/perplexity_flutter)
+
+**Examples:**
+- [Flutter Example App](https://github.com/vishnu32510/perplexity_dart/tree/main/example_flutter_app)
+- [Dart Examples](https://github.com/vishnu32510/perplexity_dart/tree/main/example)
+
+**Contributing:** Issues and PRs welcome on both repositories.