feat: add Alembic database migrations

Replace create_all() startup approach with Alembic for proper schema
versioning. Includes initial migration for users and evotor_connections
tables, entrypoint script that runs migrations before starting uvicorn.

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

Dockerfile.web

@@ -6,5 +6,8 @@ COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
 
 COPY web/ ./web/
+COPY alembic.ini .
+COPY docker-entrypoint.sh .
+RUN chmod +x docker-entrypoint.sh
 
-CMD ["uvicorn", "web.main:app", "--host", "0.0.0.0", "--port", "8000"]
+CMD ["./docker-entrypoint.sh"]