chore: add Docker dev files and ignore .sql database dumps

Added Dockerfile.dev for backend and frontend, docker-compose.dev.yml
for local development. Added *.sql to .gitignore to prevent accidental
commit of database dumps.

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

backend/Dockerfile.dev

@@ -0,0 +1,15 @@
+FROM python:3.12-slim
+
+WORKDIR /app
+
+RUN apt-get update && apt-get install -y \
+    gcc \
+    libpq-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY requirements.txt requirements-dev.txt ./
+RUN pip install --no-cache-dir -r requirements-dev.txt
+
+EXPOSE 8000
+
+CMD [ "uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000", "--reload" ]