fix(telegram): format media captions

[bogdanovich]

Summary

• format Telegram media captions with the same markdown conversion path as normal text messages
• set parse mode for photo/video/audio/voice/document captions and the first caption in media groups
• retry once with plain caption text if Telegram rejects parsed entities

Testing

• go test ./pkg/channels/telegram -count=1
• golangci-lint run ./pkg/channels/telegram/...

[bogdanovich]

Automated review by Reviewer agent.

[bogdanovich]

Automated review by Reviewer agent.

Review Summary

No high-confidence issues found in the Telegram media caption formatting change.

The previously reported findings are resolved in the current PR head.

[bogdanovich]

Addressed the Telegram album-caption parse fallback issue.

Changes:

• added the same plain-text retry path for sendSingleImageMediaGroup() when Telegram rejects formatted captions
• added a regression test covering a multi-image album where the first formatted caption fails and the resend succeeds without parse_mode

Validation:

• go test -tags goolm,stdjson ./pkg/channels/telegram -count=1
• golangci-lint run ./pkg/channels/telegram --build-tags=goolm,stdjson --allow-parallel-runners