feat: add rate limiting, retry with backoff, and max count cap

- Add configurable request delay between paginated API calls (default 1.5s)
- Add retry with exponential backoff on HTTP 429 and Twitter error code 88
- Add hard max count cap (default 200, absolute ceiling 500)
- Add rateLimit config section with requestDelay, maxRetries, retryBaseDelay, maxCount
- Add normalization tests for rateLimit config

config.yaml

@@ -13,3 +13,9 @@ filter:
     replies: 2.0
     bookmarks: 5.0
     views_log: 0.5
+
+rateLimit:
+  requestDelay: 1.5    # seconds between paginated requests
+  maxRetries: 3        # retry count on 429 / rate-limit errors
+  retryBaseDelay: 5.0  # base delay for exponential backoff (seconds)
+  maxCount: 200        # hard cap for single fetch