perf(backend): raise mobile Go memory limit 150MB -> 1GB — undersized limit forced permanent GC thrash (#21470-hf)

The 150MB soft memory limit sat ~3x below the service process's measured
working set (350-620MB while syncing a large community), forcing the Go GC
into permanent maximum-aggression mode. A/B on a Samsung S21FE running the
identical 9-day community sync (~1.7GB ingested, all other #21470 fixes in
place): with the 150MB limit the GC consumed 61% of service CPU and the
process ran at 150-390% CPU; with the limit lifted the same walk ran at
46-127% CPU and GC left the profile's top consumers entirely, at a peak RSS
of 621MB (bounded independently by the hash-first ingest backpressure). 1GB
retains an OOM guard well above the working set without starving the GC.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
(cherry picked from commit 8d13821)
(cherry picked from commit ad0e2350b27dbf2dca2c756388295f81e45dc62b)

Author: alexjba

pkg/backend/geth_backend.go

@@ -125,7 +125,15 @@ func NewStatusBackend(logger *zap.Logger) *StatusBackend {
 		zap.String("IpfsGatewayURL", gocommon.IpfsGatewayURL))
 
 	if gocommon.IsMobilePlatform() {
-		debug.SetMemoryLimit(1024 * 1024 * 150) // 150MB
+		// #21470: the previous 150MB soft limit sat ~3x below the measured
+		// working set (350-620MB while syncing a large community), which forces
+		// the Go GC into permanent maximum-aggression mode. Measured on a
+		// Samsung S21FE (identical 9-day community sync, ~1.7GB ingested):
+		// with 150MB the GC was 61% of service CPU and the process ran at
+		// 150-390% CPU; with the limit lifted the same walk ran at 46-127%
+		// CPU with GC no longer in the profile's top consumers. 1GB keeps an
+		// OOM guard well above the working set without starving the GC.
+		debug.SetMemoryLimit(1024 * 1024 * 1024) // 1GB
 	}
 
 	return backend