chore: bump pydantic/ty and expand README

[lorr1]

Summary

• Bump pydantic to >=2.13.2 (resolves to 2.13.3) and ty to >=0.0.31 (resolves to 0.0.32). Supersedes Renovate Update dependency pydantic to >=2.13.3 #26 and Update dependency ty to >=0.0.32 #30.
• Expand the README so a new user can tell at a glance that this is a template, how to point a client at the server, how token passthrough works, and how it fits with ToolHive.

Details

Dependency bumps

• pydantic: >=2.12.5 → >=2.13.2
• ty: >=0.0.28 → >=0.0.31
• uv.lock refreshed accordingly.

README additions

• Banner at the top making it explicit that the template does nothing useful until edited, and pointing at the Client Setup section.
• Client Setup section: endpoint (/mcp), Authorization: Bearer header, example client JSON, and pointers to the files that own endpoint/auth config.
• How Token Passthrough Works section: describes that TokenPassthroughMiddleware extracts but does not validate the token, shows how tools read it via get_bearer_token(), and calls out that this is not an authorization layer.
• Using with ToolHive section linking to https://github.com/stacklok/toolhive, since this template is meant to run behind ToolHive (which handles the real token validation / policy / audit).

Test plan

• task lint passes
• task typecheck passes
• task test — 11 unit tests pass, 3 integration tests skipped (server not running, expected)
• Reviewer: skim the README render on GitHub to confirm the new sections read well