Refactor send() to module-level send_telegram_message() for testability

Extract the nested send() function into a module-level
send_telegram_message(bot_token, chat_id, text, timeout=10)
function. This enables unit testing without hitting the real
Telegram API.

Changes:
- Add send_telegram_message() at module level in TELEGRAM section
- Replace nested send() with thin wrapper that calls
  send_telegram_message()
- Update argparse --telegram help text to use TELEGRAM_BOT_TOKEN
- Add tests/test_browse.py with 8 unit tests covering:
  - Success case (returns message_id)
  - API error (RuntimeError)
  - Invalid token (HTTPError 404)
  - Rate limit (HTTPError 429)
  - Network error (URLError)
  - Timeout (URLError)
  - Custom timeout parameter
  - HTML parse_mode in request

Ref: #4

skills/polymarket-browse/tests/__init__.py

@@ -0,0 +1 @@
+# Tests package