PHASE 2: Implements balance assertions for reconciliation

Adds balance assertion functionality to enable admins to verify accounting accuracy.

This includes:
- A new `balance_assertions` table in the database
- CRUD operations for balance assertions (create, get, list, check, delete)
- API endpoints for managing balance assertions (admin only)
- UI elements for creating, viewing, and re-checking assertions

Also, reorders the implementation roadmap in the documentation to reflect better the dependencies between phases.

migrations.py

@@ -270,3 +270,51 @@ async def m006_hierarchical_account_names(db):
             """,
             {"new_name": new_name, "id": account["id"]}
         )
+
+
+async def m007_balance_assertions(db):
+    """
+    Create balance_assertions table for reconciliation.
+    Allows admins to assert expected balances at specific dates.
+    """
+    await db.execute(
+        f"""
+        CREATE TABLE balance_assertions (
+            id TEXT PRIMARY KEY,
+            date TIMESTAMP NOT NULL,
+            account_id TEXT NOT NULL,
+            expected_balance_sats INTEGER NOT NULL,
+            expected_balance_fiat TEXT,
+            fiat_currency TEXT,
+            tolerance_sats INTEGER DEFAULT 0,
+            tolerance_fiat TEXT DEFAULT '0',
+            checked_balance_sats INTEGER,
+            checked_balance_fiat TEXT,
+            difference_sats INTEGER,
+            difference_fiat TEXT,
+            status TEXT NOT NULL DEFAULT 'pending',
+            created_by TEXT NOT NULL,
+            created_at TIMESTAMP NOT NULL DEFAULT {db.timestamp_now},
+            checked_at TIMESTAMP,
+            FOREIGN KEY (account_id) REFERENCES accounts (id)
+        );
+        """
+    )
+
+    await db.execute(
+        """
+        CREATE INDEX idx_balance_assertions_account_id ON balance_assertions (account_id);
+        """
+    )
+
+    await db.execute(
+        """
+        CREATE INDEX idx_balance_assertions_status ON balance_assertions (status);
+        """
+    )
+
+    await db.execute(
+        """
+        CREATE INDEX idx_balance_assertions_date ON balance_assertions (date);
+        """
+    )