bundle Adwaita symbolic icons in gresource

On macOS the Adwaita icon theme is not installed by default, so
symbolic icons (edit-copy, auth-fingerprint, network-wired,
dialog-warning, etc.) render as the "image-missing" placeholder.

Bundle the symbolic SVGs used by the GTK frontend into the embedded
gresource so the app is self-contained and doesn't depend on any
system-installed icon theme. The existing
`IconTheme::add_resource_path("/de/feschber/LanMouse/icons")` call
already tells GTK to search this prefix, so no code changes are
needed.

Icons are sourced from Adwaita and placed under the standard
`scalable/{actions,devices,places,status}/` hicolor layout.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lan-mouse-gtk/resources/icons/scalable/status/dialog-warning-symbolic.svg

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg height="16px" viewBox="0 0 16 16" width="16px" xmlns="http://www.w3.org/2000/svg">
+    <path d="m 7.90625 0.09375 c -0.527344 -0.0273438 -1.039062 0.28125 -1.4375 0.96875 l -6.25 11.59375 c -0.535156 0.964844 0.046875 2.34375 1.09375 2.34375 h 13.15625 c 0.980469 0 1.902344 -1.160156 1.21875 -2.34375 l -6.3125 -11.53125 c -0.398438 -0.644531 -0.941406 -1.003906 -1.46875 -1.03125 z m 1.09375 3.90625 v 5 c 0.007812 0.527344 -0.472656 1 -1 1 s -1.007812 -0.472656 -1 -1 v -5 z m -1 7 c 0.550781 0 1 0.449219 1 1 s -0.449219 1 -1 1 s -1 -0.449219 -1 -1 s 0.449219 -1 1 -1 z m 0 0" fill="#2e3436"/>
+</svg>

lan-mouse-gtk/resources/icons/scalable/status/network-wired-disconnected-symbolic.svg

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg height="16px" viewBox="0 0 16 16" width="16px" xmlns="http://www.w3.org/2000/svg">
+    <g fill="#2e3436">
+        <path d="m 15 10 c 0.265625 0 0.519531 0.105469 0.707031 0.292969 c 0.390625 0.390625 0.390625 1.023437 0 1.414062 l -1.292969 1.292969 l 1.292969 1.292969 c 0.390625 0.390625 0.390625 1.023437 0 1.414062 s -1.023437 0.390625 -1.414062 0 l -1.292969 -1.292969 l -1.292969 1.292969 c -0.390625 0.390625 -1.023437 0.390625 -1.414062 0 s -0.390625 -1.023437 0 -1.414062 l 1.292969 -1.292969 l -1.292969 -1.292969 c -0.390625 -0.390625 -0.390625 -1.023437 0 -1.414062 c 0.1875 -0.1875 0.441406 -0.292969 0.707031 -0.292969 s 0.519531 0.105469 0.707031 0.292969 l 1.292969 1.292969 l 1.292969 -1.292969 c 0.1875 -0.1875 0.441406 -0.292969 0.707031 -0.292969 z m 0 0"/>
+        <path d="m 6 0 c -0.554688 0 -1 0.445312 -1 1 v 3 c 0 0.554688 0.445312 1 1 1 h 1 v 2 h -7 v 2 h 2 v 2 h -1 c -0.554688 0 -1 0.445312 -1 1 v 3 c 0 0.554688 0.445312 1 1 1 h 4 c 0.554688 0 1 -0.445312 1 -1 v -3 c 0 -0.554688 -0.445312 -1 -1 -1 h -1 v -2 h 12 v -2 h -7 v -2 h 1 c 0.554688 0 1 -0.445312 1 -1 v -3 c 0 -0.554688 -0.445312 -1 -1 -1 z m 0 0" fill-opacity="0.34902"/>
+    </g>
+</svg>