v0.12.4 — 15 bug fixes (CRITICAL/HIGH/MEDIUM)

CRITICAL:
- C1: SetAppBackupBulk data loss + nil map panic (settings.go)
- C2: UpdateStackConfig nil Env map panic (deploy.go)
- C3: ValidateDump missing scanner.Err() check (dbdump.go)

HIGH:
- H1: nextDailyRun DST bug — use time.Date(day+1) not Add(24h)
- H2: Cache Europe/Budapest timezone with sync.Once in scheduler
- H3: settings.save() leaks .tmp file on WriteFile failure
- H4: SetNotificationPrefs nil pointer panic
- H5: appDirSize + getDirSizeBytes ignore Sscanf return value
- H6: getDirSizeBytes has no timeout — add 30s context
- H7: dbdump.go tmpFile not using defer Close
- H8: UpdateCrossDriveStatus misleading comment

MEDIUM:
- M1: Replace custom containsBytes with strings.Contains
- M2: scheduler.Every() validates interval > 0
- M3: executeJob panic recovery now sets LastRun
- M4: logPostStartStatus copies env slice before goroutine
- M5: Cache timezone in web package via getTimezone() sync.Once

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

controller/internal/stacks/manager.go

@@ -628,10 +628,12 @@ func truncateStr(s string, maxLen int) string {
 // logPostStartStatus queries container states after a start/deploy operation
 // and logs them. This runs asynchronously to avoid blocking the HTTP response.
 func (m *Manager) logPostStartStatus(name, stackDir string, env []string) {
+	envCopy := make([]string, len(env))
+	copy(envCopy, env)
 	go func() {
 		time.Sleep(3 * time.Second)
 
-		output, err := m.composeExecCustomEnv(stackDir, env, "ps", "-a", "--format", "table {{.Name}}\t{{.Image}}\t{{.State}}\t{{.Status}}")
+		output, err := m.composeExecCustomEnv(stackDir, envCopy, "ps", "-a", "--format", "table {{.Name}}\t{{.Image}}\t{{.State}}\t{{.Status}}")
 		if err != nil {
 			m.logger.Printf("[WARN] Post-start status check failed for %s: %v", name, err)
 			return