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/config.py

@@ -0,0 +1,22 @@
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(env_file=".env", env_file_encoding="utf-8")
+
+    secret_key: str
+    database_url: str
+
+    google_client_id: str = ""
+    google_client_secret: str = ""
+    google_redirect_uri: str = ""
+
+    vapid_public_key: str = ""
+    vapid_private_key: str = ""
+    vapid_subject: str = "mailto:you@example.com"
+
+    session_cookie_name: str = "habit_session"
+    timezone: str = "Asia/Seoul"
+
+
+settings = Settings()