Enhance admin bootstrap process with reset functionality

- Update .env.example and README.md to include new ADMIN_BOOTSTRAP_RESET option for resetting admin credentials on startup.
- Modify main.py to implement logic for resetting the admin's password, role, and status if ADMIN_BOOTSTRAP_RESET is set to true.
- Adjust config.py to define the new setting, ensuring proper configuration management.

app/main.py

@@ -97,6 +97,12 @@ def _bootstrap_admin() -> None:
     try:
         existing = db.query(User).filter(User.email == settings.admin_bootstrap_email).first()
         if existing:
+            if settings.admin_bootstrap_reset:
+                existing.password_hash = hash_password(settings.admin_bootstrap_password)
+                existing.is_admin = True
+                existing.role = "admin"
+                existing.is_active = True
+                db.commit()
             return
         user = User(
             email=settings.admin_bootstrap_email,