fix: improve online IP report handling

[besnow]

Motivation

• Ensure online-IP reporting errors are not swallowed and avoid POSTing empty online-IP payloads while preserving existing production logic and API contracts.
• Allow limiter to use real node protocol type to decide online-IP recording entry for certain protocols (hysteria2/tuic) with a minimal, non-invasive change.
• Risk: enabling hysteria2/tuic in the online-IP path may make DeviceLimit/online-IP behavior more sensitive and should be observed after rollout.

Description

• Fix ReportNodeOnlineUsers to return err when checkResponse fails by changing api/panel/user.go to return err instead of return nil.
• Prevent empty online-IP payloads by adding len(data) != 0 guard in node/user.go before calling ReportNodeOnlineUsers and add a concise debug log when filtering results in zero reported entries.
• Add Nodetype string to Limiter, change AddLimiter signature to AddLimiter(nodetype string, tag string, ...) and initialize Nodetype in limiter/limiter.go.
• Make CheckLimit consider hysteria2 and tuic for online-IP recording by updating the condition to if noSSUDP || l.Nodetype == "hysteria2" || l.Nodetype == "tuic", and update call sites in node/controller.go and node/task.go to pass node.Type/newN.Type into AddLimiter.
• Confirmations: the /api/v1/server/UniProxy/alive endpoint and payload type map[int][]string remain unchanged, and no node_type=v2node or large refactors were introduced.

Testing

• Ran gofmt -w on modified files successfully.
• Ran go build ./... and the build completed successfully.
• Verified changes via git diff --stat and ensured the diff shows only the intended minimal modifications and no interface or payload changes.

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Codex Task