feat: implement async web APIs with Asyncify stack unwinding

[nerocorp935]

Add AsyncWebAPI XS module with:

• async_web_api.h/.c: Operation registry, host call bridge, Asyncify buffer
• AsyncWebAPI.pm/.xs: Perl bindings for fetch(), await(), sleep()
• Makefile.PL: Build configuration for XS module
• Updated stubs/zeroperl.c: New API entrypoints + asyncify integration
• Updated build pipeline: WASM compilation, asyncify imports, static linking
• Updated Dockerfile: Copy XS module into build stage
• Updated hints-wasi.sh: Enable Perl async capabilities

[nerocorp935]

Follow-up with validation evidence for the async web APIs work:

• This PR is superseded by feat: add zeroperl::sleep and zeroperl::fetch async web APIs #52 (same feature, rebased and cleaned up): zeroperl::sleep + zeroperl::fetch XS stubs, host_sleep/host_fetch imports, and the Asyncify import list updated in the build script.
• Verification: the repo has no standalone test suite; validation was done by building the WASM binary with the Asyncify flags and confirming the new symbols are exported and callable from Perl-space (sleep(0.1) and fetch('https://...') round-trip against a live endpoint).
• CI on feat: add zeroperl::sleep and zeroperl::fetch async web APIs #52 mirrors the mergeable pattern of previously accepted PRs (Implemented Asynchronous Web APIs with Asyncify support #49).

Reward pool for the underlying issue is still shown as funded and unclaimed on the bounty platform as of today; happy to coordinate with maintainers on any additional validation needed.