Add tabbed code examples (show multiple providers side by side)

[AmitoVrito]

Description

Use Docusaurus tabs to show the same example across different LLM providers.

What to do

• Use Tabs component from @docusaurus/theme-classic
• Show tabs: OpenAI | Anthropic | Ollama | Gemini on quickstart and provider pages

[AmitoVrito]

Thanks for your interest! I will assign it to you. Before you start, could you give the repo a ⭐ on the main repo (https://github.com/SynapseKit/SynapseKit)? It really helps with visibility for a new project. Looking forward to your PR!