Fix news engine (keywords, calendar fallback, RSS URL), remove Telegram guards

News engine: expand sentiment keywords (18%→60% headline coverage), add
MyFXBook RSS as fallback calendar source when Forex Factory returns 429,
add retry/backoff on calendar API rate limits, update stale ForexLive URL
to investinglive.com, add date formats without seconds for MyFXBook RSS.

Telegram bot: remove flood control, rate limiter, and dashboard failure
tracking — all sends go directly through bot.send_message/edit_message_text.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

config.py

@@ -123,7 +123,7 @@ class NewsConfig:
     post_event_buffer_minutes: int = 15
 
     rss_feeds: List[str] = field(default_factory=lambda: [
-        "https://www.forexlive.com/feed/",
+        "https://investinglive.com/feed/",
         "https://www.fxstreet.com/rss",
     ])