feat: Upgrade FastMCP to 3.2.0

[clareliguori]

FastMCP has a vulnerability of 'critical' severity that is blocking my release pipeline. This PR upgrades FastMCP to the patcher version (3.2.0), including changes required to upgrade from 2.x to 3.x.

The major change I made is to remove the AWSMCPProxy and AWSProxyToolManager classes. We can now use FastMCPProxy directly. FastMCP 3.x includes built-in tool caching with a 5-minute TTL via ProxyProvider, making our custom caching logic unnecessary.

Other breaking changes in FastMCP 2.x -> 3.x:

• get_tools() renamed to list_tools() and returns list instead of dict
• Proxy module moved from fastmcp.server.proxy to fastmcp.server.providers.proxy
• on_initialize middleware return type changed to InitializeResult | None
• Tool import path changed from fastmcp.tools.tool to fastmcp.tools
• ctx.set_state() and ctx.get_state() are now async

Fixes #215

Acknowledgment

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