refactor(server): remove Run/Option, use Start/Done/Wait/Shutdown

[wc4440222]

Summary

Per @hao022 feedback on #311, this PR removes the legacy Run function and Option type from internal/server, aligning huatuo-bamai with the same Start → Done/Wait → Shutdown pattern used by huatuo-apiserver.

Changes

internal/server/server.go

• Remove Run, run, and Option type
• Remove unused backoff and syscall imports

cmd/huatuo-bamai/handlers/server.go

• Start now returns (RunningServer, error) instead of nothing
• Uses httpServer.Start(opts.Addr) instead of s.Run(&Option{...})
• Remove EnableRetry from config (no longer needed)
• Add RunningServer interface (matching apiserver pattern)

cmd/huatuo-bamai/tracing.go

• startHandlers saves the returned RunningServer to d.apiServer
• Registers runningServer.Shutdown as daemon cleanup

cmd/huatuo-bamai/main.go

• Add apiServer field to Daemon struct
• waitForSignal now monitors apiServer.Done() for unexpected exits
• Returns (os.Signal, error) to propagate serve errors

Reference

This follows the pattern in cmd/huatuo-apiserver/ where:

1. handlers.Start returns (RunningServer, error)
2. startHandlers saves the server and registers Shutdown as cleanup
3. Daemon.waitForSignal monitors server.Done()