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/static/manifest.json

@@ -0,0 +1,17 @@
+{
+  "name": "습관 트래커",
+  "short_name": "습관 트래커",
+  "description": "형성하고 싶은 습관과 끊고 싶은 습관을 요일별로 관리하고 매일 체크하는 개인용 습관 관리 앱",
+  "start_url": "/today",
+  "scope": "/",
+  "display": "standalone",
+  "orientation": "portrait",
+  "background_color": "#f5f4ef",
+  "theme_color": "#d97757",
+  "lang": "ko",
+  "icons": [
+    { "src": "/static/icons/icon-192.png", "sizes": "192x192", "type": "image/png", "purpose": "any" },
+    { "src": "/static/icons/icon-512.png", "sizes": "512x512", "type": "image/png", "purpose": "any" },
+    { "src": "/static/icons/icon-maskable-512.png", "sizes": "512x512", "type": "image/png", "purpose": "maskable" }
+  ]
+}