Rename project to GoSentry

Rename the application, Go module path, command package, build artifacts, resource script, and embedded icon assets from PySentry/pysentry to GoSentry/gosentry.

Move portable settings to gosentry.yaml while reading legacy pysentry.yaml during the transition, then rewrite settings under the new name.

Update Windows and Linux autostart integration to use GoSentry names while cleaning up legacy PySentry registry, desktop-entry, and systemd artifacts.

Refresh README, architecture notes, roadmap, changelog, and release examples for version 0.3.0.

cmd/gosentry/main.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"os"
+
+	"gitea.mixdep.ru/mix/gosentry/src/core"
+	"gitea.mixdep.ru/mix/gosentry/src/gui"
+)
+
+func main() {
+	// The executable entry point intentionally delegates all startup work to the
+	// GUI package. Keeping main small makes it easier to add platform-specific
+	// packaging later without mixing window setup, storage, and scheduler logic.
+	gui.Run(hasArgument(core.StartInTrayArgument))
+}
+
+func hasArgument(argument string) bool {
+	for _, current := range os.Args[1:] {
+		if current == argument {
+			return true
+		}
+	}
+	return false
+}