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/habits.html

@@ -0,0 +1,32 @@
+{% extends "base.html" %}
+{% block title %}습관 관리 · 습관 트래커{% endblock %}
+{% block nav_habits %}active{% endblock %}
+{% block content %}
+<h1>습관 관리</h1>
+
+<div class="tabs">
+  <a href="/habits?tab=build" class="{{ 'active' if tab == 'build' }}">만들고 싶은 습관</a>
+  <a href="/habits?tab=quit" class="{{ 'active' if tab == 'quit' }}">멈추고 싶은 습관</a>
+  <a href="/habits?tab=completed" class="{{ 'active' if tab == 'completed' }}">완료된 습관</a>
+</div>
+
+{% if tab in ("build", "quit") %}
+  {% include "partials/habit_form.html" %}
+{% endif %}
+
+<div class="card">
+  {% if habits %}
+    <div id="habit-list">
+    {% for habit in habits %}
+      {% include "partials/habit_item.html" %}
+    {% endfor %}
+    </div>
+  {% else %}
+    <div class="empty-state">
+      {% if tab == "build" %}만들고 싶은 습관이 아직 없어요. 위에서 추가해보세요.
+      {% elif tab == "quit" %}끊고 싶은 습관이 아직 없어요. 위에서 추가해보세요.
+      {% else %}아직 완료된 습관이 없어요.{% endif %}
+    </div>
+  {% endif %}
+</div>
+{% endblock %}