`pprof` exposure (Middlewares — P2)

  - **What:** Small adapter that mounts `net/http/pprof` handlers under a configurable prefix.
  - **Why Middlewares:** Operational/diagnostic, not used in all deployments.
  - **Precedents:** Standard `net/http/pprof`; Echo and Fiber provide wrappers. (<https://pkg.go.dev/net/http/pprof>, <https://docs.gofiber.io/api/middleware/pprof/>)
