Phase 1.1: Add exchange configuration

- Add exchange constants to shared/constants.json:
  - eurTradeMin: 100, eurTradeMax: 3000, eurTradeIncrement: 20
  - premiumPercentage: 5
  - priceRefreshSeconds: 60, priceStalenessSeconds: 300
- Add exchangeStatuses and tradeDirections to shared constants
- Add ExchangeStatus and TradeDirection enums to models.py
- Update shared_constants.py to export new exchange constants
- Update validate_constants.py to validate new enums and fields

backend/validate_constants.py

@@ -3,7 +3,14 @@
 import json
 from pathlib import Path
 
-from models import ROLE_ADMIN, ROLE_REGULAR, AppointmentStatus, InviteStatus
+from models import (
+    ROLE_ADMIN,
+    ROLE_REGULAR,
+    AppointmentStatus,
+    ExchangeStatus,
+    InviteStatus,
+    TradeDirection,
+)
 
 
 def validate_shared_constants() -> None:
@@ -44,6 +51,24 @@ def validate_shared_constants() -> None:
             f"Expected: {expected_appointment_statuses}, Got: {got}"
         )
 
+    # Validate exchange statuses
+    expected_exchange_statuses = {s.name: s.value for s in ExchangeStatus}
+    if constants.get("exchangeStatuses") != expected_exchange_statuses:
+        got = constants.get("exchangeStatuses")
+        raise ValueError(
+            f"Exchange status mismatch. "
+            f"Expected: {expected_exchange_statuses}, Got: {got}"
+        )
+
+    # Validate trade directions
+    expected_trade_directions = {d.name: d.value for d in TradeDirection}
+    if constants.get("tradeDirections") != expected_trade_directions:
+        got = constants.get("tradeDirections")
+        raise ValueError(
+            f"Trade direction mismatch. "
+            f"Expected: {expected_trade_directions}, Got: {got}"
+        )
+
     # Validate booking constants exist with required fields
     booking = constants.get("booking", {})
     required_booking_fields = [
@@ -56,6 +81,20 @@ def validate_shared_constants() -> None:
         if field not in booking:
             raise ValueError(f"Missing booking constant '{field}' in constants.json")
 
+    # Validate exchange constants exist with required fields
+    exchange = constants.get("exchange", {})
+    required_exchange_fields = [
+        "eurTradeMin",
+        "eurTradeMax",
+        "eurTradeIncrement",
+        "premiumPercentage",
+        "priceRefreshSeconds",
+        "priceStalenessSeconds",
+    ]
+    for field in required_exchange_fields:
+        if field not in exchange:
+            raise ValueError(f"Missing exchange constant '{field}' in constants.json")
+
     # Validate validation rules exist (structure check only)
     validation = constants.get("validation", {})
     required_fields = ["telegram", "signal", "nostrNpub"]