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/models/habit_log.py

@@ -0,0 +1,19 @@
+from datetime import date, datetime
+
+from sqlalchemy import Date, ForeignKey, Integer, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class HabitLog(Base):
+    __tablename__ = "habit_log"
+    __table_args__ = (UniqueConstraint("habit_id", "log_date", name="uq_habit_log_habit_date"),)
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    habit_id: Mapped[int] = mapped_column(ForeignKey("habit.id", ondelete="CASCADE"), nullable=False)
+    log_date: Mapped[date] = mapped_column(Date, nullable=False)
+    checked_at: Mapped[datetime] = mapped_column(server_default=func.now(), nullable=False)
+
+    habit: Mapped["Habit"] = relationship(back_populates="logs")