feat: add image_path to recipe/subtask and user password change API

- Recipe model: add image_path field for recipe-level image
- RecipeSubtask model: add image_path for per-subtask detail images
- Schemas: add image_path to create/update/response for recipe and subtask
- Task router: pass image_path when creating tasks and subtasks
- Recipe service: copy image_path in versioning and update-in-place
- Users router: add PUT /{user_id}/password endpoint (admin only)
- User schema: add UserPasswordChange model

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

server/schemas/user.py

@@ -52,6 +52,11 @@ class UserResponse(BaseModel):
     last_login: Optional[datetime] = None
 
 
+class UserPasswordChange(BaseModel):
+    """Schema for changing user password (admin only)."""
+    password: str = Field(..., min_length=6, max_length=128)
+
+
 class LoginRequest(BaseModel):
     """Schema for login request."""
     username: str