Add Telegram album sending tool

[JosXa]

Summary

Adds a send_album media tool that sends 2-10 local files as a single Telegram media group while reusing the existing allowed-root file validation used by send_file.

Testing

PYTHONPATH=/projects/telegram-mcp.worktrees/send-album /projects/telegram-mcp/.venv/bin/python -m pytest /projects/telegram-mcp.worktrees/send-album/tests/test_media_album.py

[chigwell]

@JosXa, thank you for the contribution! Could I please ask you to fix the black formatting so the CI tests will pass? Thank you!

[konser80]

Tested this approach end-to-end and it works great — sent a real 9-photo album to a public group via Telethon's client.send_file(entity, [paths], caption=...), which is exactly what this PR wraps. All 9 images arrived as a single media group with the caption on the first item. 👍

One small thought for consideration: instead of (or in addition to) a separate send_album tool, send_file's file_path could accept Union[str, List[str]] — a list triggers album mode, a string keeps the current behavior. That avoids a second tool while staying backward-compatible. Either way, having album support merged would be very welcome.

[JosXa]

Thanks @konser80 — I incorporated your suggestion: send_file now accepts either a single path or a list of 2–10 paths, with a list delegating to album/media-group mode while preserving the existing single-file behavior. I kept send_album as an explicit convenience tool as well.

Also addressed the earlier formatting/CI concern from @chigwell.

Verification performed locally:

• uv run pytest tests/test_media_album.py tests/test_install_guard.py -q → 15 passed
• uv run black --check telegram_mcp/tools/media.py tests/test_media_album.py telegram_mcp/install_guard.py tests/test_install_guard.py → unchanged
• Live Telegram check: sent a 2-photo media group to Saved Messages via send_album('me', [...]); it returned Album sent to chat me with 2 files.