Adds per-user wallet configuration

Allows users to configure their own wallet ID, enabling
the system to track expenses and receivables on a per-user basis.

Introduces new database table, models, API endpoints, and UI elements
to manage user-specific wallet settings.

services.py

@@ -1,9 +1,12 @@
 from .crud import (
     create_castle_settings,
+    create_user_wallet_settings,
     get_castle_settings,
+    get_user_wallet_settings,
     update_castle_settings,
+    update_user_wallet_settings,
 )
-from .models import CastleSettings
+from .models import CastleSettings, UserWalletSettings
 
 
 async def get_settings(user_id: str) -> CastleSettings:
@@ -21,3 +24,22 @@ async def update_settings(user_id: str, data: CastleSettings) -> CastleSettings:
         settings = await update_castle_settings(user_id, data)
 
     return settings
+
+
+async def get_user_wallet(user_id: str) -> UserWalletSettings:
+    settings = await get_user_wallet_settings(user_id)
+    if not settings:
+        settings = await create_user_wallet_settings(user_id, UserWalletSettings())
+    return settings
+
+
+async def update_user_wallet(
+    user_id: str, data: UserWalletSettings
+) -> UserWalletSettings:
+    settings = await get_user_wallet_settings(user_id)
+    if not settings:
+        settings = await create_user_wallet_settings(user_id, data)
+    else:
+        settings = await update_user_wallet_settings(user_id, data)
+
+    return settings