Integrate FastMCP

This commit integrates FastMCP, a high-level MCP server implementation originally written by Jeremiah Lowin,
into the official MCP SDK. It also updates dependencies and adds new dev dependencies.
It moves the existing SDK into a .lowlevel .

src/mcp/server/fastmcp/exceptions.py

@@ -0,0 +1,21 @@
+"""Custom exceptions for FastMCP."""
+
+
+class FastMCPError(Exception):
+    """Base error for FastMCP."""
+
+
+class ValidationError(FastMCPError):
+    """Error in validating parameters or return values."""
+
+
+class ResourceError(FastMCPError):
+    """Error in resource operations."""
+
+
+class ToolError(FastMCPError):
+    """Error in tool operations."""
+
+
+class InvalidSignature(Exception):
+    """Invalid signature for use with FastMCP."""