feat(lab12): Spin WASM /time endpoint with perf and wasmtime bonus

[markovav-official]

Goal

Build a Moscow-time /time HTTP endpoint as a Spin/TinyGo WASM component, benchmark it against the Lab 6 Docker image, and compare Spin's wasi-http model with a standalone wasmtime run module.

Changes

• Add wasm/ — Spin Go SDK component (spin.toml, main.go, go.mod) serving JSON at GET /time
• Add wasm-cli/ — bonus standalone WASI module (CGI-style) runnable under wasmtime run
• Add submissions/lab12.md with design answers (a–j) and perf table
• Add submissions/attachments/lab12/ — build logs, curl output, hyperfine JSON, cold-start samples
• Add cloud/scripts/lab12-vm-*.sh — VM toolchain setup and benchmark scripts

Testing

• University VM: spin build → 354 KB main.wasm; spin up + curl /time → valid Moscow JSON
• Bonus: tinygo build -target=wasi → wasmtime run --env REQUEST_METHOD=GET --env PATH_INFO=/time → same JSON
• Perf vs Lab 6 Docker (quicknotes:lab6): 3.8 MB vs 354 KB; warm p50 7.1 ms vs 9.4 ms; cold p50 1.4 s vs 12.9 s (constrained 1.8 GiB VM)
• Bonus cold: wasmtime run ~12 ms per invocation

Checklist

• Title is a clear sentence (≤ 70 chars)
• Commits are signed (git log --show-signature)
• submissions/lab12.md updated