v0.5.1 — Windows icon fix

Windows icons.

sendmecongo moves files out of a physically isolated machine in one direction only — a fountain-coded QR stream on the screen, a phone camera on the other side, and a byte-identical file at the end. No network, no USB, no Bluetooth.

Changes in v0.5.1

Both icons were missing on Windows, and both went missing without saying anything.

• The .exe file icon. winres emits cargo:rustc-link-lib=static=resource on the GNU toolchain, and GNU ld only pulls an archive member in when it resolves an undefined symbol. A pure resource object defines none, so the resource — the icon and the version block — was dropped silently, leaving no .rsrc section in the binary at all. The compiled resource.o is now handed to the linker directly; the guard keeps MSVC, which produces resource.lib instead, on its original path. A resource compile failure panics now instead of being swallowed by let _ =.
• The window icon. with_icon(egui::IconData::default()) is deliberate on macOS — it stops eframe from overwriting the bundle's AppIcon.icns — but a bare .exe has no bundle behind it, so the title bar and the taskbar drew the generic application glyph even once the file icon was right. The same app.ico the build script embeds is now decoded for the window, and every non-Windows target still gets the empty icon it got before.

No protocol, codec or layout change — on macOS both fixes either compile out or return exactly what they returned before.

109 tests green across the workspace, plus a clean cargo check --workspace --target x86_64-pc-windows-msvc --no-default-features.

Assets — macOS (Apple Silicon, .app inside a DMG)

File	Size	SHA-256
sendmecongo-send-0.5.1.dmg	4.42 MB	E032E5E4040D01F4FA0755E1CD926559247126C5F9D83B7511970D9800AE09E3
sendmecongo-recv-0.5.1.dmg	4.71 MB	0A3B15A952320202C709D1A8FB4AC4DB0DCA844196B2A6A6DFEAA3E14CF5E767

Assets — Windows x86_64, standalone exe

These were built from this same icon fix and are hosted on the v0.5.0 page, which is the release number they carry.

File	Size	SHA-256
sendmecongo-send.exe	18.51 MB	207996AE9D63D56C2918376D07759A98E6DA3DAA9B428FD9576EE3220CA2C4DB
sendmecongo-recv.exe	19.90 MB	B7466EE2B0F97137FED4C0D86EA070436BC3B4824F82EDC96910912D83BACC31