Add token lifecycle management to client.tokens (refresh/revoke/scopes/copy)

[sandshoes]

Summary

• The SDK can create JWTs and declare static tokens (define_token) but had no way to manage tokens it created afterward. Extends the existing TokensNamespace (client.tokens) with list(), get(name), scopes(name), refresh(name), revoke(name), and copy(name), matching tb token ls/rm/refresh/scopes/copy.
• Adds TinybirdApi.list_tokens(), get_token(), refresh_token(), revoke_token() wrapping GET /v0/tokens, GET/DELETE /v0/tokens/{name}, and POST /v0/tokens/{name}/refresh, following the existing create_token request-building conventions.
• Closes https://linear.app/tinybird/issue/PROTM-2266/python-sdk-add-token-lifecycle-management-refreshrevokescopescopy

Verified the real contract instead of guessing: read the vendored Forward CLI client (tinybird/tb/client.py / tinybird/tb/modules/token.py in this project's own dependency tree) to confirm endpoint paths, methods, and — importantly — what tb token copy actually does.

Note on copy: tb token copy copies the token's value to the system clipboard via pyperclip — it does not duplicate a token under a new name, as the ticket's phrasing might suggest. A library has no clipboard, so client.tokens.copy(name) returns the token's current value instead (same underlying data tb token copy puts on the clipboard), for the caller to use or store as needed. Documented clearly in the README so no one goes looking for clipboard behavior.

revoke maps to DELETE /v0/tokens/{name} — there's no separate "revoke" endpoint distinct from delete in the real API; named revoke per the ticket's own wording since that's the more accurate verb for a bearer token (there's nothing to restore).

Checklist

• CI is green (lint, typecheck, test, secrets)
• pre-commit run --all-files passes locally (gitleaks step fails in this sandbox on an unrelated SSL/network error fetching its environment — not a code issue)
• Tests were added or updated when behavior changed
• Public API / typing changes were reviewed
• Documentation was updated (README.md / CONTRIBUTING.md) if needed
• Breaking changes are clearly documented (none — purely additive)
• CHANGELOG.md was updated when user-facing behavior changed