fix(upgrade): break auto-apply restart loop (0.9.8)

Two bugs in 0.9.6/0.9.7 caused an infinite restart loop after a Force update
signal: the CLI never reported the upgrade outcome, so `upgrade_requested`
stayed `true`; AND `applyAutoUpgrade` called `os.Exit(0)` even when the
target version equalled the current one, so systemd respawned and saw the
flag again.

  - new Client.ReportUpgradeResult → POST /api/internal/agent/upgrade-result
  - applyAutoUpgrade calls it on success / failure / no-op
  - no-op case detected up front (same version) — skips Execute + Exit,
    clears server flag instead

internal/cmd/version.go

@@ -1,4 +1,4 @@
 package cmd
 
 // Version is the CLI version. Overridden by goreleaser ldflags at release time.
-var Version = "0.9.7"
+var Version = "0.9.8"