Docker builds were slow due to poor layer caching (copying all code before deps), running migrations at build time, and no .dockerignore.

Changes

• Added .dockerignore — excludes .git/, screenshots/, terraform/, docs, and build artifacts (~1MB+ reduction in build context)

• Optimized Dockerfile:

  • Switch from alpine:latest to python:3.11-slim (specific version, smaller image)
  • Copy requirements.txt first, install deps, then copy code (enables dependency layer caching)
  • Move migrate to container startup via CMD (was baked into build)
  • Remove duplicate psycopg2 install (already in requirements.txt) and unused Pillow
  • Consolidate RUN commands and clean apt cache in same layer

# Before: deps reinstalled on every code change
COPY . /app
RUN pip install -r requirements.txt

# After: deps cached when only code changes
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .

• Fixes Painful Build #61

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