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>

app/templates/today.html

@@ -0,0 +1,8 @@
+{% extends "base.html" %}
+{% block title %}오늘 · 습관 트래커{% endblock %}
+{% block nav_today %}active{% endblock %}
+{% block content %}
+<div id="today-content">
+  {% include "partials/today_content.html" %}
+</div>
+{% endblock %}