feat: initial implementation — Arte Concert web GUI

FastAPI backend + HTML/JS frontend pour parcourir et télécharger les
concerts Arte Concert. Cache 6h, recherche live, historique SQLite,
suivi de progression SSE, design sombre Playfair Display + Inter.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,14 @@
+FROM python:3.12-slim
+
+WORKDIR /app
+
+RUN apt-get update -qq && apt-get install -y -qq ffmpeg && rm -rf /var/lib/apt/lists/*
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . .
+
+EXPOSE 8080
+
+CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8080"]