Add "Skip TLS Verification" toggle to Provider Settings

[jax256]

Is your feature request related to a problem? Please describe.
Users behind strict SNI filtering or DNS blocks often need to connect to Usenet providers using direct IP addresses. However, when using a direct IP in the Host field with SSL enabled, nzbdav rejects the connection due to a Certificate Hostname Mismatch.

Describe the solution you'd like
Please add a "Skip TLS Verification" checkbox in the Add/Edit Provider UI. When enabled, allowing secure connections directly to the IP.

Describe alternatives you've considered
VPN Proxying: Routing the container through a VPN bypasses the block but introduces unnecessary network overhead and reduces maximum download speeds.

Additional context
Adding a per-provider TLS skip toggle would make nzbdav significantly more resilient for users operating in restrictive network environments. Thank you for your work on this project!