feat: Flask front-end with clockwise-rotating cats

[Copilot]

Flask equivalent of the Streamlit front/ app, living in front-flask/. Adds clockwise-spinning cat emoji animations on every page.

Structure

• app.py – three routes: / (home), /predict (GET + POST → FastAPI /predict_one), /visualize
• templates/ – Jinja2 templates extending a shared base.html navbar
• static/style.css – layout + @keyframes spin-cw (positive rotate() = clockwise); each .cat runs at a slightly different duration (2.5–5 s) for variety
• requirements.txt – flask, requests only
• Dockerfile – python:3.11-slim, exposes 5000

Cats (clockwise rotation)

@keyframes spin-cw {
    from { transform: rotate(0deg); }
    to   { transform: rotate(360deg); }
}
.cat { animation: spin-cw linear infinite; }
.cat:nth-child(1) { animation-duration: 3s; }
/* … up to 5s */

Notable

• API_HOST read from env (default http://localhost:8888), matching the Streamlit convention
• Visualize page renders charts client-side via Plotly.js CDN — no server-side data processing needed
• Debug mode off by default; opt-in via FLASK_DEBUG=true

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