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.sum

@@ -9,6 +9,8 @@ github.com/BurntSushi/toml v1.6.0 h1:dRaEfpa2VI55EwlIW72hMRHdWouJeRF7TPYhI+AUQjk
 github.com/BurntSushi/toml v1.6.0/go.mod h1:ukJfTF/6rtPPRCnwkur4qwRxa8vTRFBF0uk2lLoLwho=
 github.com/DATA-DOG/go-sqlmock v1.5.2 h1:OcvFkGmslmlZibjAjaHm3L//6LiuBgolP7OputlJIzU=
 github.com/DATA-DOG/go-sqlmock v1.5.2/go.mod h1:88MAG/4G7SMwSE3CeA0ZKzrT5CiOU3OJ+JlNzwDqpNU=
+github.com/SevereCloud/vksdk/v3 v3.3.1 h1:O86zsp5LQnHE+O5acvuXM/s6S1LyxzVTkF6+Lup0Jyg=
+github.com/SevereCloud/vksdk/v3 v3.3.1/go.mod h1:c6WaA5aocUYsXfkcUbg2qy45V9M1VDcqHHmHIN14NAw=
 github.com/adhocore/gronx v1.19.6 h1:5KNVcoR9ACgL9HhEqCm5QXsab/gI4QDIybTAWcXDKDc=
 github.com/adhocore/gronx v1.19.6/go.mod h1:7oUY1WAU8rEJWmAxXR2DN0JaO4gi9khSgKjiRypqteg=
 github.com/agnivade/levenshtein v1.2.1 h1:EHBY3UOn1gwdy/VbFwgo4cxecRznFk7fKWN1KOX7eoM=
@@ -274,6 +276,10 @@ github.com/valyala/fastjson v1.6.10 h1:/yjJg8jaVQdYR3arGxPE2X5z89xrlhS0eGXdv+ADT
 github.com/valyala/fastjson v1.6.10/go.mod h1:e6FubmQouUNP73jtMLmcbxS6ydWIpOfhz34TSfO3JaE=
 github.com/vektah/gqlparser/v2 v2.5.27 h1:RHPD3JOplpk5mP5JGX8RKZkt2/Vwj/PZv0HxTdwFp0s=
 github.com/vektah/gqlparser/v2 v2.5.27/go.mod h1:D1/VCZtV3LPnQrcPBeR/q5jkSQIPti0uYCP/RI0gIeo=
+github.com/vmihailenco/msgpack/v5 v5.4.1 h1:cQriyiUvjTwOHg8QZaPihLWeRAAVoCpE00IUPn0Bjt8=
+github.com/vmihailenco/msgpack/v5 v5.4.1/go.mod h1:GaZTsDaehaPpQVyxrf5mtQlH+pc21PIudVV/E3rRQok=
+github.com/vmihailenco/tagparser/v2 v2.0.0 h1:y09buUbR+b5aycVFQs/g70pqKVZNBmxwAhO7/IwNM9g=
+github.com/vmihailenco/tagparser/v2 v2.0.0/go.mod h1:Wri+At7QHww0WTrCBeu4J6bNtoV6mEfg5OIWRZA9qds=
 github.com/xyproto/randomstring v1.0.5 h1:YtlWPoRdgMu3NZtP45drfy1GKoojuR7hmRcnhZqKjWU=
 github.com/xyproto/randomstring v1.0.5/go.mod h1:rgmS5DeNXLivK7YprL0pY+lTuhNQW3iGxZ18UQApw/E=
 github.com/yeongaori/discordgo-fork v0.0.0-20260319072544-e8e546f5d532 h1:gxFHYeUDGziRb0zXYEqBFohC+NJbIW9L0tddaXMWr2o=