Fix: Dockerfile Python modules path and CMD syntax

- Use virtual environment instead of --user install
  - Fix PATH to /opt/venv/bin (accessible by appuser)
  - Fix CMD syntax with shell form
  - Add curl for healthcheck
  - Proper init_db.py execution before uvicorn

ebook_backend&admin_panel/Dockerfile

@@ -9,13 +9,17 @@ RUN apt-get update && apt-get install -y \
     gcc \
     postgresql-client \
     libpq-dev \
+    curl \
     && rm -rf /var/lib/apt/lists/*
 
 # Kopírovanie requirements
 COPY requirements.txt .
 
-# Inštalácia Python dependencies
-RUN pip install --no-cache-dir --user -r requirements.txt
+# Inštalácia Python dependencies do /opt/venv
+RUN python -m venv /opt/venv
+ENV PATH="/opt/venv/bin:$PATH"
+RUN pip install --no-cache-dir --upgrade pip && \
+    pip install --no-cache-dir -r requirements.txt
 
 # Production stage
 FROM python:3.11-slim
@@ -23,12 +27,13 @@ FROM python:3.11-slim
 # Nastavenie environment variables
 ENV PYTHONUNBUFFERED=1 \
     PYTHONDONTWRITEBYTECODE=1 \
-    PATH=/root/.local/bin:$PATH
+    PATH="/opt/venv/bin:$PATH"
 
 # Inštalácia runtime dependencies
 RUN apt-get update && apt-get install -y \
     postgresql-client \
     libpq-dev \
+    curl \
     && rm -rf /var/lib/apt/lists/*
 
 # Vytvorenie non-root user pre bezpečnosť
@@ -37,8 +42,8 @@ RUN useradd -m -u 1000 appuser
 # Nastavenie working directory
 WORKDIR /app
 
-# Kopírovanie Python dependencies z builder stage
-COPY --from=builder /root/.local /root/.local
+# Kopírovanie Python virtual environment z builder stage
+COPY --from=builder /opt/venv /opt/venv
 
 # Kopírovanie aplikačných súborov
 COPY --chown=appuser:appuser . .
@@ -56,9 +61,10 @@ EXPOSE 8000
 
 # Healthcheck
 HEALTHCHECK --interval=30s --timeout=10s --start-period=40s --retries=3 \
-    CMD python -c "import requests; requests.get('http://localhost:8000/health')" || exit 1
+    CMD curl -f http://localhost:8000/health || exit 1
 
 # Spustenie aplikácie
 WORKDIR /app/admin-backend
-CMD ["python", "init_db.py"] && \
-    ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000", "--workers", "4"]
+
+# Použijeme shell form aby sme mohli spustiť init_db.py a potom uvicorn
+CMD ["/bin/sh", "-c", "python init_db.py && uvicorn main:app --host 0.0.0.0 --port 8000 --workers 4"]