feat: AI photo enhancement (Real-ESRGAN container) + restore original

- new photo-ai service: FastAPI + Real-ESRGAN x2plus on CPU, internal only
- async job queue in server (POST enhance-ai / GET status), 5min timeout, sequential processing
- keep original photo backup (entries.photo_original_path, uploads/.originals), restore-original endpoint
- UI: AI button and restore-original button in enhance modal
- db: photo_original_path column (init.sql, migration.sql, runtime ensure)

photo-ai/Dockerfile

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+FROM python:3.10-slim
+
+WORKDIR /app
+
+RUN apt-get update && apt-get install -y --no-install-recommends libgl1 libglib2.0-0 && rm -rf /var/lib/apt/lists/*
+
+RUN pip install --no-cache-dir torch torchvision --index-url https://download.pytorch.org/whl/cpu
+
+RUN pip install --no-cache-dir realesrgan==0.3.0 fastapi "uvicorn[standard]" python-multipart opencv-python-headless numpy
+
+RUN python - <<'EOF'
+import basicsr, os
+p = os.path.join(os.path.dirname(basicsr.__file__), 'data', 'degradations.py')
+s = open(p).read()
+s = s.replace('torchvision.transforms.functional_tensor', 'torchvision.transforms.functional')
+open(p, 'w').write(s)
+print('basicsr patch applied')
+EOF
+
+COPY app.py .
+
+ENV MODEL_PATH=/models/RealESRGAN_x2plus.pth
+
+VOLUME /models
+
+CMD ["uvicorn", "app:app", "--host", "0.0.0.0", "--port", "8080"]