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/devices/auth-fingerprint-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 8.074219 0 c -1.203125 -0.0117188 -2.40625 0.285156 -3.492188 0.890625 c -0.480469 0.269531 -0.652343 0.878906 -0.382812 1.359375 c 0.269531 0.484375 0.878906 0.65625 1.359375 0.386719 c 1.550781 -0.867188 3.4375 -0.847657 4.972656 0.050781 c 1.53125 0.898438 2.46875 2.535156 2.46875 4.3125 v 1 c 0 0.550781 0.449219 1 1 1 s 1 -0.449219 1 -1 v -1 c 0 -0.019531 0 -0.039062 -0.003906 -0.054688 c -0.019532 -2.460937 -1.332032 -4.738281 -3.457032 -5.984374 c -1.070312 -0.628907 -2.265624 -0.9492192 -3.46875 -0.960938 z m -5.199219 2.832031 c -0.066406 0 -0.132812 0.007813 -0.195312 0.023438 c -0.257813 0.058593 -0.484376 0.21875 -0.625 0.445312 c -0.6875 1.109375 -1.054688 2.390625 -1.054688 3.699219 v 5.0625 c 0 0.550781 0.449219 1 1 1 s 1 -0.449219 1 -1 v -5.0625 c 0 -0.933594 0.261719 -1.851562 0.753906 -2.644531 c 0.292969 -0.46875 0.148438 -1.082031 -0.320312 -1.375 c -0.167969 -0.105469 -0.363282 -0.15625 -0.558594 -0.148438 z m 5.125 0.167969 c -2.199219 0 -4 1.800781 -4 4 v 1 c 0 0.550781 0.449219 1 1 1 s 1 -0.449219 1 -1 v -1 c 0 -1.117188 0.882812 -2 2 -2 s 2 0.882812 2 2 v 5 s 0.007812 0.441406 0.175781 0.941406 s 0.5 1.148438 1.117188 1.765625 c 0.390625 0.390625 1.023437 0.390625 1.414062 0 s 0.390625 -1.023437 0 -1.414062 c -0.382812 -0.382813 -0.550781 -0.734375 -0.632812 -0.984375 s -0.074219 -0.308594 -0.074219 -0.308594 v -5 c 0 -2.199219 -1.800781 -4 -4 -4 z m 0 3 c -0.550781 0 -1 0.449219 -1 1 v 5 s 0 0.59375 0.144531 1.320312 c 0.144531 0.726563 0.414063 1.652344 1.148438 2.386719 c 0.390625 0.390625 1.023437 0.390625 1.414062 0 s 0.390625 -1.023437 0 -1.414062 c -0.265625 -0.265625 -0.496093 -0.839844 -0.601562 -1.363281 c -0.105469 -0.523438 -0.105469 -0.929688 -0.105469 -0.929688 v -5 c 0 -0.550781 -0.449219 -1 -1 -1 z m -3 4 c -0.550781 0 -1 0.449219 -1 1 v 3 c 0 0.550781 0.449219 1 1 1 s 1 -0.449219 1 -1 v -3 c 0 -0.550781 -0.449219 -1 -1 -1 z m 9 0 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="#2e3434"/>
+</svg>

lan-mouse-gtk/resources/icons/scalable/devices/network-wired-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 6 0.015625 c -0.554688 0 -1 0.445313 -1 1 v 3 c 0 0.554687 0.445312 1 1 1 h 1 v 2 h -7 v 2 h 2 v 2 h -1 c -0.554688 0 -1 0.445313 -1 1 v 3 c 0 0.554687 0.445312 1 1 1 h 4 c 0.554688 0 1 -0.445313 1 -1 v -3 c 0 -0.554687 -0.445312 -1 -1 -1 h -1 v -2 h 8 v 2 h -1 c -0.554688 0 -1 0.445313 -1 1 v 3 c 0 0.554687 0.445312 1 1 1 h 4 c 0.554688 0 1 -0.445313 1 -1 v -3 c 0 -0.554687 -0.445312 -1 -1 -1 h -1 v -2 h 2 v -2 h -7 v -2 h 1 c 0.554688 0 1 -0.445313 1 -1 v -3 c 0 -0.554687 -0.445312 -1 -1 -1 z m 0 0" fill="#2e3436"/>
+</svg>