P5: per-platform transparent, size-appropriate window/tray icons

Give the window titlebar, taskbar, and tray a size-appropriate icon with a
transparent boundary on both Windows and Linux, instead of scaling one PNG to
every size.

Assets:
- Regenerate the PNGs and gosentry.ico with feathered color-to-alpha so the
  rounded-tile boundary is transparent; a binary white-key had left an opaque
  halo that read as a border on dark taskbars/trays.
- Rebuild gosentry.ico as multi-size (16 hand-tuned + 32/48/256 from big) and
  add a single-frame 16x16 gosentry-icon-16x16.ico for the Windows tray.
- assets.go: add IconSmall() and IconSmallICO().

Wiring:
- Windows window/taskbar: embed gosentry.ico under the GLFW_ICON resource and
  skip a.SetIcon so GLFW selects the right frame per size (hand-tuned 16 for the
  titlebar, a larger frame for the taskbar).
- Windows tray: SetSystemTrayIcon(IconSmallICO()), a 16x16 ICO frame.
- Linux window titlebar: a.SetIcon(IconSmall()) for a crisp ~16px _NET_WM_ICON;
  tray uses the big PNG since StatusNotifierItem renders larger.

Also bump Fyne 2.6.3 -> 2.7.4 (systray 1.11.0 -> 1.12.1) and document the full
cross-platform icon strategy in assets.go, gosentry.rc, run.go, and tray.go.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

go.mod

@@ -3,38 +3,40 @@ module gitea.mixdep.ru/mix/gosentry
 go 1.22
 
 require (
-	fyne.io/fyne/v2 v2.6.3
+	fyne.io/fyne/v2 v2.7.4
 	github.com/robfig/cron/v3 v3.0.1
 	go.yaml.in/yaml/v4 v4.0.0-rc.5
 )
 
 require (
-	fyne.io/systray v1.11.0 // indirect
-	github.com/BurntSushi/toml v1.4.0 // indirect
+	fyne.io/systray v1.12.1 // indirect
+	github.com/BurntSushi/toml v1.5.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/fredbi/uri v1.1.0 // indirect
+	github.com/fredbi/uri v1.1.1 // indirect
 	github.com/fsnotify/fsnotify v1.9.0 // indirect
 	github.com/fyne-io/gl-js v0.2.0 // indirect
 	github.com/fyne-io/glfw-js v0.3.0 // indirect
 	github.com/fyne-io/image v0.1.1 // indirect
-	github.com/fyne-io/oksvg v0.1.0 // indirect
+	github.com/fyne-io/oksvg v0.2.0 // indirect
 	github.com/go-gl/gl v0.0.0-20231021071112-07e5d0ea2e71 // indirect
 	github.com/go-gl/glfw/v3.3/glfw v0.0.0-20240506104042-037f3cc74f2a // indirect
-	github.com/go-text/render v0.2.0 // indirect
-	github.com/go-text/typesetting v0.2.1 // indirect
+	github.com/go-text/render v0.2.1 // indirect
+	github.com/go-text/typesetting v0.3.4 // indirect
 	github.com/godbus/dbus/v5 v5.1.0 // indirect
 	github.com/hack-pad/go-indexeddb v0.3.2 // indirect
 	github.com/hack-pad/safejs v0.1.0 // indirect
 	github.com/jeandeaual/go-locale v0.0.0-20250612000132-0ef82f21eade // indirect
 	github.com/jsummers/gobmp v0.0.0-20230614200233-a9de23ed2e25 // indirect
 	github.com/kr/text v0.2.0 // indirect
+	github.com/mattn/go-runewidth v0.0.17 // indirect
 	github.com/nfnt/resize v0.0.0-20180221191011-83c6a9932646 // indirect
 	github.com/nicksnyder/go-i18n/v2 v2.5.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/rymdport/portal v0.4.1 // indirect
+	github.com/rivo/uniseg v0.2.0 // indirect
+	github.com/rymdport/portal v0.4.2 // indirect
 	github.com/srwiley/oksvg v0.0.0-20221011165216-be6e8873101c // indirect
 	github.com/srwiley/rasterx v0.0.0-20220730225603-2ab79fcdd4ef // indirect
-	github.com/stretchr/testify v1.10.0 // indirect
+	github.com/stretchr/testify v1.11.1 // indirect
 	github.com/yuin/goldmark v1.7.8 // indirect
 	golang.org/x/image v0.24.0 // indirect
 	golang.org/x/net v0.35.0 // indirect