Add ValuationCollector class that fetches PER, PBR, and dividend yield
data from KRX for all listed stocks. Includes business day validation,
safe float conversion, and upsert logic for the valuations table.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Implement StockCollector to fetch stock master data from KRX
(Korea Exchange) including market cap, EPS, BPS, and dividend info.
Implement SectorCollector to fetch WICS sector classification from
WISEindex. Both collectors use PostgreSQL upsert for efficient updates.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
