Add NextSnap PWA with photo gallery viewer and continuous capture

Offline-first photo capture app for Nextcloud with:
- Camera capture with continuous mode (auto-reopens after each photo)
- File browser with fullscreen image gallery, swipe navigation, and rename
- Upload queue with background sync engine
- Admin panel for Nextcloud user management
- Service worker for offline-first caching (v13)

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

Dockerfile

@@ -0,0 +1,45 @@
+FROM python:3.11-slim
+
+# Set working directory
+WORKDIR /app
+
+# Install system dependencies
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    curl \
+    libheif-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install Python dependencies
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+# Copy application code
+COPY . .
+
+# Create directories for runtime data
+RUN mkdir -p /tmp/flask_session && \
+    chmod 777 /tmp/flask_session
+
+# Create non-root user for security
+RUN useradd -m -u 1000 nextsnap && \
+    chown -R nextsnap:nextsnap /app /tmp/flask_session
+
+USER nextsnap
+
+# Expose port
+EXPOSE 8000
+
+# Health check
+HEALTHCHECK --interval=30s --timeout=10s --retries=3 \
+    CMD curl -f http://localhost:8000/api/health || exit 1
+
+# Use gunicorn for production with app factory
+CMD ["gunicorn", \
+     "--workers", "4", \
+     "--bind", "0.0.0.0:8000", \
+     "--timeout", "120", \
+     "--access-logfile", "-", \
+     "--error-logfile", "-", \
+     "--log-level", "info", \
+     "app:create_app()"]