Add SSID-based Wi-Fi network exclusion for DNS protection (feature parity with Windows/iOS)

### Issue Details

AdGuard for Windows (Advanced Settings → "Wi-Fi networks excluded from DNS protection," specified by SSID) and AdGuard for iOS (DNS protection → Network settings → "Wi-Fi exceptions") both let users disable DNS filtering on specific named Wi-Fi networks — for example, a home or work network that already has its own DNS-level filtering (e.g., AdGuard Home), where AdGuard's own DNS filtering becomes redundant or conflicts.
AdGuard for Android currently has no equivalent. The closest options in Low-level settings are:
Excluded apps (by package name/UID)
IPv4/IPv6 ranges excluded from filtering
Route all LAN IPv4 connections
None of these let you target a specific Wi-Fi network by SSID.

### Proposed solution

Add a "Wi-Fi networks excluded from DNS protection" field under Low-level settings → DNS protection, matching the existing Windows implementation: a text field where SSIDs can be entered one per line, and DNS filtering is automatically skipped whenever the device is connected to a matching network.

### Alternative solution

Excluding the network's IP subnet range, which works only if the subnet is stable and unique to that network.
Third-party automation (Tasker/MacroDroid) to toggle protection on SSID change, which is fragile and not officially supported.