feat: add rate limiting for overseas market scanning (issue #51)

Add 200ms delay between overseas API calls to prevent hitting
KIS API rate limit (EGW00201: 초당 거래건수 초과).

Changes:
- src/analysis/scanner.py:79-81 - Add asyncio.sleep(0.2) for overseas calls

Impact:
- EGW00201 errors eliminated during market scanning
- Scan completion time increases by ~1.2s for 6 stocks
- Trade-off: Slower scans vs complete market data

Before: Multiple EGW00201 errors, incomplete scans
After: Clean scans, all stocks processed successfully

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/analysis/scanner.py

@@ -76,6 +76,10 @@ class MarketScanner:
             if market.is_domestic:
                 orderbook = await self.broker.get_orderbook(stock_code)
             else:
+                # Rate limiting: Add 200ms delay for overseas API calls
+                # to prevent hitting KIS API rate limit (EGW00201)
+                await asyncio.sleep(0.2)
+
                 # For overseas, we need to adapt the price data structure
                 price_data = await self.overseas_broker.get_overseas_price(
                     market.exchange_code, stock_code