Step 5: Update exchange price endpoint to use new pricing config

- Update ExchangeConfigResponse schema with direction-specific fields
- Remove premium_percentage from PriceResponse (now in config)
- Update price endpoint to load pricing config from database
- Update frontend to use direction-specific min/max and calculate premium
- Update tests to seed pricing config
- Add logic to clamp amount when direction changes

backend/routes/exchange.py

@@ -20,6 +20,7 @@ from models import (
 from price_fetcher import PAIR_BTC_EUR, SOURCE_BITFINEX, fetch_btc_eur_price
 from repositories.exchange import ExchangeRepository
 from repositories.price import PriceRepository
+from repositories.pricing import PricingRepository
 from schemas import (
     AdminExchangeResponse,
     AvailableSlotsResponse,
@@ -31,12 +32,7 @@ from schemas import (
     UserSearchResult,
 )
 from services.exchange import ExchangeService
-from shared_constants import (
-    EUR_TRADE_INCREMENT,
-    EUR_TRADE_MAX,
-    EUR_TRADE_MIN,
-    PREMIUM_PERCENTAGE,
-)
+from shared_constants import EUR_TRADE_INCREMENT
 from utils.enum_validation import validate_enum
 
 router = APIRouter(prefix="/api/exchange", tags=["exchange"])
@@ -65,20 +61,33 @@ async def get_exchange_price(
 
     The response includes:
     - market_price: The raw price from the exchange
-    - premium_percentage: The premium to apply to trades
     - is_stale: Whether the price is older than 5 minutes
-    - config: Trading configuration (min/max EUR, increment)
+    - config: Trading configuration (min/max EUR per direction, premiums, increment)
     """
-    config = ExchangeConfigResponse(
-        eur_min=EUR_TRADE_MIN,
-        eur_max=EUR_TRADE_MAX,
-        eur_increment=EUR_TRADE_INCREMENT,
-        premium_percentage=PREMIUM_PERCENTAGE,
-    )
-
     price_repo = PriceRepository(db)
+    pricing_repo = PricingRepository(db)
     service = ExchangeService(db)
 
+    # Load pricing config from database
+    pricing_config = await pricing_repo.get_current()
+    if pricing_config is None:
+        raise HTTPException(
+            status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
+            detail="Pricing configuration not available",
+        )
+
+    config = ExchangeConfigResponse(
+        eur_min_buy=pricing_config.eur_min_buy,
+        eur_max_buy=pricing_config.eur_max_buy,
+        eur_min_sell=pricing_config.eur_min_sell,
+        eur_max_sell=pricing_config.eur_max_sell,
+        eur_increment=EUR_TRADE_INCREMENT,
+        premium_buy=pricing_config.premium_buy,
+        premium_sell=pricing_config.premium_sell,
+        small_trade_threshold_eur=pricing_config.small_trade_threshold_eur,
+        small_trade_extra_premium=pricing_config.small_trade_extra_premium,
+    )
+
     # Try to get the latest cached price
     cached_price = await price_repo.get_latest()
 
@@ -101,7 +110,6 @@ async def get_exchange_price(
             return ExchangePriceResponse(
                 price=PriceResponse(
                     market_price=price_value,
-                    premium_percentage=PREMIUM_PERCENTAGE,
                     timestamp=timestamp,
                     is_stale=False,
                 ),
@@ -113,7 +121,6 @@ async def get_exchange_price(
                 return ExchangePriceResponse(
                     price=PriceResponse(
                         market_price=cached_price.price,
-                        premium_percentage=PREMIUM_PERCENTAGE,
                         timestamp=cached_price.timestamp,
                         is_stale=True,
                     ),
@@ -131,7 +138,6 @@ async def get_exchange_price(
     return ExchangePriceResponse(
         price=PriceResponse(
             market_price=cached_price.price,
-            premium_percentage=PREMIUM_PERCENTAGE,
             timestamp=cached_price.timestamp,
             is_stale=service.is_price_stale(cached_price.timestamp),
         ),