Add animated FastAPI demo + correct the multi-stack install table

[Anioko]

What

1. Animated terminal demo (demo.svg, embedded at the top of the README): PRD → generated FastAPI app (with the file tree shown) → docker compose up → Swagger /docs → register / create / list / auth-refusal. demo.cast is the reproducible asciinema v2 source. Renders inline on GitHub — no click-through.
2. Honest install table: marked FastAPI as the verified reference; removed install commands for packages that are not actually published and labelled them 🚧 coming soon.

Why the install table changed (verified against the live registries)

Stack	Registry check	Action
FastAPI pip install archiet-microcodegen	PyPI 200, boots end-to-end	kept, marked ✅ reference
Flask / Django / NestJS / Laravel / .NET / Go	registry 200	kept
Rails gem install …-rails	rubygems 404	→ coming soon
Tauri cargo install …-tauri	crates.io 404	→ coming soon
Spring Boot java -jar …	no registry artifact	→ coming soon

HN clicks these. A gem install that 404s in the top comment is worse than an honest "coming soon".

Dogfood check

The demo is real: I ran archiet-microcodegen 0.2.2 on examples/sample-prd.md, booted the result in Docker, and walked register (201) → create (201, user-scoped) → list (200) → no-cookie (401) → /docs (200). Every line in the animation is captured from that run.

⚠️ Depends on archiet-microcodegen 0.2.2 being published. The 0.1/0.2.1 releases generate a FastAPI app whose schema never gets created (no migration runs on docker compose up) and hit a passlib/bcrypt crash on register — so the current ./demo.sh shows Swagger then 500s on the first API call. 0.2.2 (built + verified, awaiting the PyPI token) fixes both. Merge this once 0.2.2 is live.