Still model | Delete Feature

User Story

As a user, you should be able to delete stills from your gallery using a valid still ID. If the still ID is present, it will be deleted from the gallery; otherwise, it will display an invalid still delete message. Please note that you need to provide a valid still ID to delete the image from your gallery.

### DAO:

- [x] deleteStill()

### Service:

- [x] deleteStill()

### Service Tests:

- [x] testStilldeleteSuccess()

### Flow

```mermaid
graph TD
A[Start] --> B([User Initiates Still Delete])
B --> C([Check If Still id Exists])
C --> |Still Id Is Not Found|H([Validation Exception])
C --> |Display Delete Confirmation| D([Still Confirms Delete])
D --> |Still Details Confirms| E[(Delete Still)]
E --> |Return true| F[Still Deleted Successfully]
E --> |Fail| G[Failed to Delete Still]
H --> G
F --> I[End]
G --> I

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