fix: properly close telegram client session to prevent resource leak (issue #52)

Adds telegram.close() to finally block to ensure aiohttp session cleanup.

Changes:
- src/main.py:553 - Add await telegram.close() in shutdown

Before:
- broker.close() called ✅
- telegram.close() NOT called ❌
- "Unclosed client session" error on shutdown

After:
- broker.close() called ✅
- telegram.close() called ✅
- Clean shutdown, no resource leak errors

Impact:
- Eliminates aiohttp resource leak warnings
- Proper cleanup of Telegram API connections
- No memory leaks in long-running processes

Related:
- KISBroker.close() already handles broker session
- OverseasBroker reuses KISBroker session (no separate close needed)
- TelegramClient has separate session that needs cleanup

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/main.py

@@ -549,7 +549,9 @@ async def run(settings: Settings) -> None:
             except TimeoutError:
                 pass  # Normal — timeout means it's time for next cycle
     finally:
+        # Clean up resources
         await broker.close()
+        await telegram.close()
         db_conn.close()
         logger.info("The Ouroboros rests.")