Add dockerized app and infra scaffolding

app/backend/Dockerfile

@@ -0,0 +1,63 @@
+# Backend image for FastAPI + LiveKit Agent runtime
+# Supports dev (uvicorn reload) and production (gunicorn) via APP_ENV.
+
+# Builder: install deps with uv into an isolated venv
+FROM python:3.12-slim AS builder
+
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    UV_PROJECT_ENV=/opt/venv
+
+# System packages needed for common Python builds + uv installer
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends build-essential curl && \
+    rm -rf /var/lib/apt/lists/*
+
+# Install uv (fast Python package manager) as the dependency tool
+RUN curl -LsSf https://astral.sh/uv/install.sh | sh
+ENV PATH="/root/.local/bin:${PATH}"
+
+# Create virtualenv and prepare workspace
+RUN python -m venv ${UV_PROJECT_ENV}
+ENV PATH="${UV_PROJECT_ENV}/bin:${PATH}"
+WORKDIR /app
+
+# Copy the full source; dependency install is guarded to avoid failures while the app is scaffolded
+COPY . /app
+RUN if [ -f uv.lock ] && [ -f pyproject.toml ]; then \
+        uv sync --frozen --no-dev; \
+    elif ls requirements*.txt >/dev/null 2>&1; then \
+        for req in requirements*.txt; do \
+            uv pip install --no-cache -r "$req"; \
+        done; \
+    elif [ -f pyproject.toml ]; then \
+        uv pip install --no-cache .; \
+    else \
+        echo "No dependency manifest found; skipping install"; \
+    fi && \
+    if [ -f pyproject.toml ]; then \
+        uv pip install --no-cache -e .; \
+    fi
+
+# Runtime: slim image with non-root user and prebuilt venv
+FROM python:3.12-slim AS runtime
+
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    PATH="/opt/venv/bin:${PATH}"
+
+# Create unprivileged user
+RUN addgroup --system app && adduser --system --ingroup app app
+
+WORKDIR /app
+
+# Copy runtime artifacts from builder
+COPY --from=builder /opt/venv /opt/venv
+COPY --from=builder /app /app
+RUN chown -R app:app /app /opt/venv
+
+USER app
+EXPOSE 8000
+
+# Default command switches between uvicorn (dev) and gunicorn (prod) based on APP_ENV
+CMD ["sh", "-c", "if [ \"$APP_ENV\" = \"production\" ]; then exec gunicorn app.main:app -k uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000 --workers 4 --timeout 120; else exec uvicorn app.main:app --host 0.0.0.0 --port 8000 --reload; fi"]