Adds manual payment request functionality

Enables users to request manual payments from the Castle and provides admin functions to approve or reject these requests.

Introduces the `manual_payment_requests` table and related CRUD operations.
Adds API endpoints for creating, retrieving, approving, and rejecting manual payment requests.
Updates the UI to allow users to request payments and for admins to review pending requests.

migrations.py

@@ -155,3 +155,36 @@ async def m004_user_wallet_settings(db):
         );
         """
     )
+
+
+async def m005_manual_payment_requests(db):
+    """
+    Create manual_payment_requests table for user payment requests to Castle.
+    """
+    await db.execute(
+        f"""
+        CREATE TABLE manual_payment_requests (
+            id TEXT PRIMARY KEY,
+            user_id TEXT NOT NULL,
+            amount INTEGER NOT NULL,
+            description TEXT NOT NULL,
+            status TEXT NOT NULL DEFAULT 'pending',
+            created_at TIMESTAMP NOT NULL DEFAULT {db.timestamp_now},
+            reviewed_at TIMESTAMP,
+            reviewed_by TEXT,
+            journal_entry_id TEXT
+        );
+        """
+    )
+
+    await db.execute(
+        """
+        CREATE INDEX idx_manual_payment_requests_user_id ON manual_payment_requests (user_id);
+        """
+    )
+
+    await db.execute(
+        """
+        CREATE INDEX idx_manual_payment_requests_status ON manual_payment_requests (status);
+        """
+    )