Fix Advertisement parsing, Windows 7 icons, and LWRP sweep hang

Created by: ykmn

Summary

• AdvertisementParser: fix a TLV parsing bug where the type byte 0x09 (the BUSY tag) was unrecognized and aborted the scan of the rest of the packet — silently dropping every source that followed the first nameless channel on a device. Also recovers PSID-only channels (no FSID), falls back to "Channel N" when PSNM is absent, and surfaces the TYPE model code for devices seen only via Advertisement.
• MainWindow.xaml: replace four toolbar icons that relied on the Segoe MDL2 Assets font (not present on Windows 7, rendered as empty boxes) with plain vector Path/Ellipse shapes that render identically on any Windows version.
• LwrpScanner/NetworkScanner: fix two bugs that could keep the brute-force TCP/93 subnet sweep from ever finishing on a real network — reverse-DNS lookups were started for every swept address (not just responding hosts) and left running detached once a host failed to connect, serializing on the OS resolver and starving the thread pool; and the 300ms per-command timeout was too short for real multi-line SRC responses, causing trailing lines to bleed into the next LWRP command and get lost. Connect and query timeouts are now separate, and DNS lookups only start after a device actually answers on TCP/93.

Test plan

• dotnet build — clean
• dotnet test tests/LivewireBrowser.Core.Tests/LivewireBrowser.Core.Tests.csproj — 97/97 passing (includes a new regression test for the BUSY-tag parsing bug)
• Ran the app and screenshotted the toolbar to confirm the new vector icons render correctly
• Re-run a full scan against the real network from the reported log to confirm devices now appear

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