Check whether an SMB Connection exists when adding; fail otherwise

Describe the bug
I tried to create an SMB Connection offline, which should have failed, but it works currently.

To Reproduce
Steps to reproduce the behavior:

1. Enter the app
2. Open "Airplane mode" (to be offline without network)
3. "+"
4. Cloud Connection
5. SMB Connection
6. USE CUSTOM IP
7. Enter any IP, Username, Password (e.g., a, a, a)
8. CREATE -> [The app hints error first time]
9. UPDATE -> [The button change from CREATE to UPDATE, and could be update successfully]
10. Repeat Step 3-8 -> [The app hints that connection already exists]

Expected behavior
The connection should be checked instead of directly succeeding and saving, e.g., invalid IP or not network should be rejected.

Screenshots

https://github.com/user-attachments/assets/266570c1-5193-4e26-8023-1d0f90d93676

Smartphone (please complete the following information):

• Device: Pixel 8
• OS: Android 14
• Rooted: No
• Version: 3.10

Additional context
I reproduced the above problem with a reinstall of the app.

Reproduce the issue in the Android app using Airplane mode, then follow the Cloud Connection > SMB Connection > USE CUSTOM IP flow through CREATE and UPDATE. Trace where the SMB connection is validated and saved, and confirm that offline or invalid connections are rejected before they are stored.