content: add hello world sample post with code demos

content/posts/hello-world.mdx

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+---
+title: "Hello, World! Building Your First TypeScript App"
+date: "2025-01-15"
+excerpt: "A beginner-friendly introduction to TypeScript with practical examples and best practices."
+---
+
+Welcome to the blog! In this post, we'll explore TypeScript from the ground up.
+
+## Why TypeScript?
+
+TypeScript adds static typing to JavaScript, catching errors at compile time rather than at runtime. Here's a simple example:
+
+```ts
+function greet(name: string): string {
+  return `Hello, ${name}!`
+}
+
+console.log(greet("World"))
+```
+
+## Type Safety in Practice
+
+Let's look at a more complex example with interfaces:
+
+```ts
+interface User {
+  id: number
+  name: string
+  email: string
+  role: "admin" | "user"
+}
+
+function createUser(data: Partial<User>): User {
+  return {
+    id: Math.random(),
+    name: data.name ?? "Anonymous",
+    email: data.email ?? "",
+    role: data.role ?? "user",
+  }
+}
+
+const user = createUser({ name: "Alice", email: "alice@example.com" })
+```
+
+## Key Concepts
+
+- **Interfaces**: Define object shapes
+- **Generics**: Create reusable components
+- **Union types**: Handle multiple possible values
+- **Type guards**: Narrow types at runtime
+
+> "TypeScript is JavaScript with syntax for types." — TypeScript Handbook
+
+## Next Steps
+
+Check out our other posts for deep dives into:
+- Mathematics with KaTeX
+- Hybrid content with code and equations