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>

migrations/versions/0004_add_user_id_columns.py

@@ -0,0 +1,41 @@
+"""add user_id to habit and push_subscription
+
+Revision ID: 0004_add_user_id_columns
+Revises: 0003_add_user_table
+Create Date: 2026-07-15
+
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0004_add_user_id_columns"
+down_revision: Union[str, None] = "0003_add_user_table"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column("habit", sa.Column("user_id", sa.Integer(), nullable=True))
+    op.create_foreign_key(
+        "fk_habit_user_id", "habit", "user", ["user_id"], ["id"], ondelete="CASCADE"
+    )
+
+    op.add_column("push_subscription", sa.Column("user_id", sa.Integer(), nullable=True))
+    op.create_foreign_key(
+        "fk_push_subscription_user_id",
+        "push_subscription",
+        "user",
+        ["user_id"],
+        ["id"],
+        ondelete="CASCADE",
+    )
+
+
+def downgrade() -> None:
+    op.drop_constraint("fk_push_subscription_user_id", "push_subscription", type_="foreignkey")
+    op.drop_column("push_subscription", "user_id")
+
+    op.drop_constraint("fk_habit_user_id", "habit", type_="foreignkey")
+    op.drop_column("habit", "user_id")