feat: improve custom jiggler settings and add timezone support (#742)

* feat: add timezone support to jiggler and fix custom settings persistence

- Add timezone field to JigglerConfig with comprehensive IANA timezone list
- Fix custom settings not loading current values
- Remove business hours preset, add as examples in custom settings
- Improve error handling for invalid cron expressions

* fix: format jiggler.go with gofmt

* fix: add embedded timezone data and validation

- Import time/tzdata to embed timezone database in binary
- Add timezone validation in runJigglerCronTab() to gracefully fallback to UTC
- Add timezone to debug logging in rpcSetJigglerConfig
- Fixes 'unknown time zone' errors when system lacks timezone data

* refactor: add timezone field comments from jiggler options

* chore: move tzdata to backend

* refactor: fix JigglerSetting linting

- Adjusted useEffect dependency to include send function for better data fetching
- Modified layout classes for improved responsiveness and consistency
- Cleaned up code formatting for better readability

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Co-authored-by: Siyuan Miao <i@xswan.net>

jsonrpc.go

@@ -1058,6 +1058,7 @@ var rpcHandlers = map[string]RPCHandler{
 	"getJigglerState":        {Func: rpcGetJigglerState},
 	"setJigglerConfig":       {Func: rpcSetJigglerConfig, Params: []string{"jigglerConfig"}},
 	"getJigglerConfig":       {Func: rpcGetJigglerConfig},
+	"getTimezones":           {Func: rpcGetTimezones},
 	"sendWOLMagicPacket":     {Func: rpcSendWOLMagicPacket, Params: []string{"macAddress"}},
 	"getStreamQualityFactor": {Func: rpcGetStreamQualityFactor},
 	"setStreamQualityFactor": {Func: rpcSetStreamQualityFactor, Params: []string{"factor"}},