Add multi-user support: Authelia OIDC, SQLite, Garage S3

- Auth via Authelia OIDC (public client + PKCE) with signed session cookies
- SQLite DB for users, rides, and insights (SQLAlchemy)
- Garage S3 for GPX file storage (boto3)
- All API endpoints scoped to authenticated user
- Dockerfile + docker-compose.yml with Garage service
- Frontend auth check: redirects to /auth/login on 401, shows user badge

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -9,4 +9,8 @@ dependencies = [
     "fastapi>=0.115.0",
     "uvicorn[standard]>=0.30.0",
     "openai>=1.50.0",
+    "sqlalchemy>=2.0.51",
+    "boto3>=1.43.66",
+    "authlib>=1.7.2",
+    "itsdangerous>=2.2.0",
 ]