Initial commit: habit tracker PWA with Google OAuth, push notifications

FastAPI + SQLAlchemy/Alembic + MariaDB backend with Jinja2/htmx/Alpine
server-rendered frontend. Multi-user via Google OAuth, daily habit
tracking, monthly/weekly history views, Web Push reminders via
APScheduler, and PWA support (manifest, service worker, offline caching).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/docker-entrypoint.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+set -e
+
+# 컨테이너 시작 시마다 마이그레이션을 적용한다. 이미 적용된 리비전은 그냥 건너뛰므로
+# 여러 번 실행해도 안전하다(idempotent).
+alembic upgrade head
+
+exec uvicorn app.main:app --host 0.0.0.0 --port 8000