refactor: Update FastMCP examples to use new import path

Update all FastMCP examples to use mcp.server.fastmcp instead of fastmcp.
Add tests to verify example servers work correctly.

Changes:
- Update import paths in all example files
- Create test_examples.py to verify functionality
- Fix test assertions to match actual response format

examples/fastmcp/desktop.py

@@ -0,0 +1,25 @@
+"""
+FastMCP Desktop Example
+
+A simple example that exposes the desktop directory as a resource.
+"""
+
+from pathlib import Path
+
+from mcp.server.fastmcp import FastMCP
+
+# Create server
+mcp = FastMCP("Demo")
+
+
+@mcp.resource("dir://desktop")
+def desktop() -> list[str]:
+    """List the files in the user's desktop"""
+    desktop = Path.home() / "Desktop"
+    return [str(f) for f in desktop.iterdir()]
+
+
+@mcp.tool()
+def add(a: int, b: int) -> int:
+    """Add two numbers"""
+    return a + b