feat: add VK channel support (#2276)

* feat: add VK channel support

- Add VK channel implementation using vksdk
- Support text messages and media attachments
- Implement Long Poll API for real-time messaging
- Add group chat support with trigger prefixes
- Add user whitelist (allow_from) configuration
- Add VK channel documentation

Files:
- pkg/channels/vk/: VK channel implementation
- pkg/config/config.go: Add VKConfig structure
- pkg/channels/manager.go: Register VK channel
- pkg/gateway/gateway.go: Import VK channel package
- docs/channels/vk/: Usage documentation

* test: add unit tests for VK channel

- Test channel initialization with various configurations
- Test allow_from whitelist functionality
- Test group trigger configuration
- Test max message length (4000 chars)
- Test message splitting logic
- Test attachment processing

All tests passing ✓

* fix: resolve linting issues in VK channel

- Format VKConfig struct tags to comply with golines
- Remove unused mu sync.Mutex field
- Remove unused stripPrefix method

All tests passing ✓

* style: format VKConfig with golines

- Align struct tags to match project style
- Match formatting with other channel configs (Telegram, etc.)
- Fix golines linting error

* style: fix struct tag formatting in config.go

* docs: update VK channel docs to use secure token storage

* feat(vk): add voice capabilities support

- Implement VoiceCapabilities() method for VK channel
- Add audio_message attachment handling in processAttachments
- Add comprehensive tests for voice capabilities
- Support both ASR (speech-to-text) and TTS (text-to-speech)

* docs: add VK channel to documentation and update voice support

- Add VK channel to README.md and README.zh.md channel lists
- Update VK channel documentation with voice message support
- Document ASR and TTS capabilities for VK channel
- Add voice transcription configuration reference

go.mod

@@ -5,6 +5,7 @@ go 1.25.8
 require (
 	fyne.io/systray v1.12.0
 	github.com/BurntSushi/toml v1.6.0
+	github.com/SevereCloud/vksdk/v3 v3.3.1
 	github.com/adhocore/gronx v1.19.6
 	github.com/anthropics/anthropic-sdk-go v1.26.0
 	github.com/atotto/clipboard v0.1.4
@@ -89,6 +90,8 @@ require (
 	github.com/segmentio/encoding v0.5.4 // indirect
 	github.com/spf13/pflag v1.0.10 // indirect
 	github.com/vektah/gqlparser/v2 v2.5.27 // indirect
+	github.com/vmihailenco/msgpack/v5 v5.4.1 // indirect
+	github.com/vmihailenco/tagparser/v2 v2.0.0 // indirect
 	go.mau.fi/libsignal v0.2.1 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/otel v1.35.0 // indirect