Bump example web frameworks to latest

- poem 1.3 -> 3 (poem_example): no code changes needed
- salvo 0.50 -> 0.93 (salvo_example): affix -> affix_state, Depot::obtain
  now returns Result, path params <id> -> {id}; rust-version -> 1.92
- axum 0.7 -> 0.8 (proxy_cloudflare_worker_example): aligns with the axum
  0.8 already used by worker, dropping the duplicate axum 0.7