Switch to Alpine Linux and improve deployment reliability

- Switch from Debian (python:3.11-slim) to Alpine (python:3.11-alpine) for better ARM64 support
- Replace apt-get with apk package manager for lighter, faster builds
- Update package dependencies for Alpine (musl-dev, postgresql-dev, linux-headers)
- Change user creation from useradd to adduser (Alpine syntax)
- Add .gitkeep files to preserve empty alembic directories in git
- Update all quickstart scripts to always rebuild containers with --build flag
- Fixes ARM64 package installation errors on Apple Silicon Macs
- Fixes missing alembic directory errors on fresh clones

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

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

Dockerfile

@@ -1,14 +1,15 @@
-FROM python:3.11-slim
+FROM python:3.11-alpine
 
 WORKDIR /app
 
-# Install system dependencies
-# Use --no-install-recommends and handle both amd64 and arm64 architectures
-RUN apt-get update && apt-get install -y --no-install-recommends \
+# Install system dependencies for Alpine
+# Alpine uses apk instead of apt-get and is lighter/faster
+RUN apk add --no-cache \
     gcc \
+    musl-dev \
+    postgresql-dev \
     postgresql-client \
-    libpq-dev \
-    && rm -rf /var/lib/apt/lists/*
+    linux-headers
 
 # Copy requirements and install Python dependencies
 COPY requirements.txt .
@@ -21,8 +22,8 @@ COPY alembic/ ./alembic/
 COPY alembic.ini .
 COPY static/ ./static/
 
-# Create non-root user
-RUN useradd -m -u 1000 appuser && chown -R appuser:appuser /app
+# Create non-root user (Alpine uses adduser instead of useradd)
+RUN adduser -D -u 1000 appuser && chown -R appuser:appuser /app
 USER appuser
 
 # Expose port