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/schemas/push.py

@@ -0,0 +1,11 @@
+from pydantic import BaseModel
+
+
+class PushKeys(BaseModel):
+    p256dh: str
+    auth: str
+
+
+class PushSubscribeRequest(BaseModel):
+    endpoint: str
+    keys: PushKeys