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.

migrations.py

@@ -140,3 +140,18 @@ async def m003_extension_settings(db):
         );
         """
     )
+
+
+async def m004_user_wallet_settings(db):
+    """
+    Create user_wallet_settings table for per-user wallet configuration.
+    """
+    await db.execute(
+        f"""
+        CREATE TABLE user_wallet_settings (
+            id TEXT NOT NULL PRIMARY KEY,
+            user_wallet_id TEXT,
+            updated_at TIMESTAMP NOT NULL DEFAULT {db.timestamp_now}
+        );
+        """
+    )