feat: add language support and onboard configuration wizard (v0.2.0)

- Add language code intelligent parsing module (internal/lang)
- Support --lang parameter for target language specification
- Support multiple language code formats (BCP47, aliases, Chinese names)
- Implement interactive onboard configuration wizard
- Update Config struct with language fields
- Add survey library dependency for interactive UI
- Improve CLI command interface
- Add comprehensive unit tests for language module
- Update documentation (AGENTS.md, changelog.md, taolun.md, memory.md)

Supported language codes:
- Standard: zh-CN, zh-TW, en-US, en-GB, ja, ko, es, fr, de
- Aliases: cn, en, jp, kr, es, fr, de
- Chinese names: chinese, english, japanese

Commands:
- yoyo "Hello world" - basic translation
- yoyo --lang=cn "Hello world" - specify target language
- yoyo onboard - start configuration wizard
- yoyo onboard --force - force reconfiguration

Version: 0.2.0

go.mod

@@ -3,6 +3,14 @@ module github.com/titor/fanyi
 go 1.26.1
 
 require (
+	github.com/AlecAivazis/survey/v2 v2.3.7 // indirect
 	github.com/joho/godotenv v1.5.1 // indirect
+	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 // indirect
+	github.com/mattn/go-colorable v0.1.2 // indirect
+	github.com/mattn/go-isatty v0.0.8 // indirect
+	github.com/mgutz/ansi v0.0.0-20170206155736-9520e82c474b // indirect
+	golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f // indirect
+	golang.org/x/term v0.0.0-20210927222741-03fcf44c2211 // indirect
+	golang.org/x/text v0.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )