fix: deep bug hunt II — concurrency, security & optimization (25 files)

Critical: watchdog mutex panic safety, SetGeoAppOverride nil guard,
SSD-only app DB restore fallback.

High: double deploy race (atomic Deploying flag), delete/remove during
deploy guard, ScanStacks overwrite protection, FileBrowser mount mutex,
PushEvent history, PushOnce error handling, DB dump sync+close before
rename, restic retry fresh context, encrypt failure logging, cross-backup
path traversal validation, deepCopyStack completeness.

Security: constant-time API key comparison, login rate limiting (5/min),
git credential masking in logs, storage path prefix traversal fix.

Concurrency: MigrateEncryption lock ordering, SubdomainInUse I/O outside
lock, scheduler late-registered jobs, SQLite WAL verification, metrics
shutdown context, telemetry scan error logging, asset sync lock scope.

Optimization: streaming file copy for DB dumps, restic stats dedup,
atomic infra config copy.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/report/pusher.go

@@ -219,6 +219,7 @@ func (p *Pusher) PushOnce(report *Report) error {
 
 	if resp.StatusCode >= 200 && resp.StatusCode < 300 {
 		p.logger.Printf("[INFO] Hub push-once sent (%d bytes)", len(data))
+		return nil
 	}
-	return nil
+	return fmt.Errorf("hub push-once: HTTP %d", resp.StatusCode)
 }