Remove mysqlclient and add Pillow dependencies

- Remove mysqlclient from requirements.txt (using PostgreSQL only)
- Add libjpeg-dev and zlib1g-dev for Pillow image processing
- Fixes build failure when installing Python packages

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Dockerfile

@@ -7,6 +7,8 @@ FROM python:3.12-slim-bookworm AS builder
 RUN apt-get update && apt-get install -y --no-install-recommends \
     gcc \
     libpq-dev \
+    libjpeg-dev \
+    zlib1g-dev \
     && rm -rf /var/lib/apt/lists/*
 
 # Install Python dependencies