fix(cache): log "caches is not defined" only once

[yuintei]

The log is repeated for every cache() call when globalThis.caches is not available. This PR ensures the message is logged only once.

$ vite

  VITE v8.0.0  ready in 675 ms

  ➜  Local:   http://localhost:5173/
  ➜  Network: use --host to expose
  ➜  press h + enter to show help
Cache Middleware is not enabled because caches is not defined.
Cache Middleware is not enabled because caches is not defined.
Cache Middleware is not enabled because caches is not defined.
Cache Middleware is not enabled because caches is not defined.
Cache Middleware is not enabled because caches is not defined.
Cache Middleware is not enabled because caches is not defined.
Cache Middleware is not enabled because caches is not defined.
Cache Middleware is not enabled because caches is not defined.
(repeats...)
Using vars defined in .env

The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code
• (N/A) Add TSDoc/JSDoc to document the code