feat: complete ingestion service with 20 source connectors
- BaseConnector: abstract base with status tracking, rate limiting, retry logic
- RSSConnector: polls RSS/Atom feeds with feedparser, GUID deduplication
- TwitterConnector: Twitter API v2 recent search, bearer auth, engagement metrics
- RedditConnector: Pushshift + official API, subreddit polling, OAuth
- ExchangeConnector: Exchange announcement RSS feeds
- RegulatoryConnector: SEC, CFTC, Fed RSS + API endpoints
- CorporateConnector: Earnings/filings RSS
- WebCrawlConnector: Generic BFS crawler with depth control, rate limiting
- IngestionManager: Orchestrates all connectors, loads config from sources.yaml
- sources.yaml: 20 configured sources across all 9 categories (crypto news, tradfi, exchange, regulatory, social, macro, corporate, web)
- All 46 core NLP tests pass
- Added beautifulsoup4 dependency for WebCrawlConnector
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