Fix duplicate-index crash in data validation, add Telegram flood control

- Move index dedup before OHLC consistency fix in _validate_and_clean
  to prevent crash when df.loc[dup_idx] returns Series instead of scalar
- Add global flood backoff: detect RetryAfter, pause all sends/edits
  until ban expires instead of retrying and escalating the ban
- Stop dashboard edit-fail → new-message spam cascade: track consecutive
  failures, only resend after 3 failed edits
- Increase dashboard refresh from 5s to 30s, min send interval to 1.5s
- Add comprehensive QA test suite (140 tests across all 7 modules)

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

data_provider.py

@@ -267,6 +267,9 @@ class ForexDataProvider:
         df = df.ffill(limit=3)
         df = df.dropna(subset=["Close"])
 
+        df = df.sort_index()
+        df = df[~df.index.duplicated(keep="last")]
+
         now = pd.Timestamp.utcnow()
         future_mask = df.index > now + pd.Timedelta(minutes=5)
         if future_mask.any():
@@ -306,9 +309,6 @@ class ForexDataProvider:
                 f"(need {min_required}). Some indicators will be partial."
             )
 
-        df = df.sort_index()
-        df = df[~df.index.duplicated(keep="last")]
-
         cleaned = original_len - len(df)
         if cleaned > 0:
             logger.info(f"{symbol}: Cleaned {cleaned}/{original_len} bars")