perf(memory): release Go heap and decoded image caches on OS memory pressure

go_backend/exports.go

@@ -2,9 +2,19 @@ package gobackend
 
 import (
 	"encoding/json"
+	"runtime/debug"
 	"strings"
 )
 
+// ReleaseMemory drops idle pooled extension runtimes, forces a GC, and
+// returns freed heap to the OS. Called from the app on OS memory pressure and
+// when backgrounded, so the Go side's RSS doesn't sit at its high-water mark
+// after large downloads/tag writes.
+func ReleaseMemory() {
+	drainAllIsolatedRuntimePools()
+	debug.FreeOSMemory()
+}
+
 func CheckAvailability(spotifyID, isrc string) (string, error) {
 	client := NewSongLinkClient()
 	availability, err := client.CheckTrackAvailability(spotifyID, isrc)