Add app icons across web, Android, and the desktop app

- Web: favicon.ico + png icons under static/, served from the site root
  and linked from every page head.
- Android: the artwork becomes the launcher icon — the 432px adaptive
  foreground over the gruvbox background, replacing the placeholder vector
  drawables.
- Desktop: the icon is the Qt window/taskbar icon (embedded via app.qrc),
  and the app is now an installable package — a wrapped binary, a
  photog.desktop entry, and hicolor icons — so `nix profile install
  ./desktop` puts "Photog" in the application menu.

desktop/CMakeLists.txt

@@ -4,6 +4,7 @@ project(photogallery_uploader LANGUAGES CXX)
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_AUTOMOC ON)
+set(CMAKE_AUTORCC ON)
 
 find_package(Qt6 REQUIRED COMPONENTS Widgets Network Concurrent)
 find_package(Qt6Keychain REQUIRED)
@@ -15,6 +16,7 @@ add_executable(uploader
     settings.cpp
     uploadclient.cpp
     imageprep.cpp
+    app.qrc
 )
 
 target_link_libraries(uploader PRIVATE
@@ -23,3 +25,14 @@ target_link_libraries(uploader PRIVATE
     Qt6::Concurrent
     Qt6Keychain::Qt6Keychain
 )
+
+# Installation — the binary, a desktop entry, and the app icon in the hicolor
+# theme, so `nix profile install ./desktop` puts "Photog" in the app menu.
+include(GNUInstallDirs)
+install(TARGETS uploader RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
+install(FILES photog.desktop DESTINATION ${CMAKE_INSTALL_DATADIR}/applications)
+foreach(sz 32 128 256 512)
+    install(FILES icons/app-${sz}.png
+            DESTINATION ${CMAKE_INSTALL_DATADIR}/icons/hicolor/${sz}x${sz}/apps
+            RENAME photog.png)
+endforeach()