Still model | Update Feature

User Story
As a user, you should be able to edit your still images by cropping them and adding filters. If the modified image details are valid, they will be stored in the still manager folder. If the details are invalid, it will show an error message stating "Invalid update still details."

### DAO:
- [x] updateStill()

### Service:

- [x] updateStill()

### Service Tests:

- [x] testStillUpdateSuccess()

### Flow

```mermaid
graph TD
A[Start] --> B([User Initiates Update Still])
B --> C[(Search Still to Update)]
C --> |Still Not Found| D{{Service Exception}}
D --> |Fail| E([Failed to Update Still])
C --> |Still Found| G([Update Still Details])
G --> |Save Modified Still In Gallery| F([Still Updated Successfully!])
E --> I[End]
F --> |Returns Still| I

style F fill:#dfd,stroke:#333
style E fill:#fdd,stroke:#333
```