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/complex_inputs.py

@@ -0,0 +1,28 @@
+"""
+FastMCP Complex inputs Example
+
+Demonstrates validation via pydantic with complex models.
+"""
+
+from pydantic import BaseModel, Field
+from typing import Annotated
+from mcp.server.fastmcp import FastMCP
+
+mcp = FastMCP("Shrimp Tank")
+
+
+class ShrimpTank(BaseModel):
+    class Shrimp(BaseModel):
+        name: Annotated[str, Field(max_length=10)]
+
+    shrimp: list[Shrimp]
+
+
+@mcp.tool()
+def name_shrimp(
+    tank: ShrimpTank,
+    # You can use pydantic Field in function signatures for validation.
+    extra_names: Annotated[list[str], Field(max_length=10)],
+) -> list[str]:
+    """List all shrimp names in the tank"""
+    return [shrimp.name for shrimp in tank.shrimp] + extra_names