Completes Phase 1: Beancount patterns adoption

Implements core improvements from Phase 1 of the Beancount patterns adoption:

- Uses Decimal for fiat amounts to prevent floating point errors
- Adds a meta field to journal entries for a full audit trail
- Adds a flag field to journal entries for transaction status
- Migrates existing account names to a hierarchical format

This commit introduces a database migration to add the `flag` and `meta` columns to the `journal_entries` table. It also includes updates to the models, CRUD operations, and API endpoints to handle the new fields.

migrations.py

@@ -177,3 +177,96 @@ async def m004_manual_payment_requests(db):
         CREATE INDEX idx_manual_payment_requests_status ON manual_payment_requests (status);
         """
     )
+
+
+async def m005_add_flag_and_meta(db):
+    """
+    Add flag and meta columns to journal_entries table.
+    - flag: Transaction status (* = cleared, ! = pending, # = flagged, x = void)
+    - meta: JSON metadata for audit trail (source, tags, links, notes)
+    """
+    await db.execute(
+        """
+        ALTER TABLE journal_entries ADD COLUMN flag TEXT DEFAULT '*';
+        """
+    )
+
+    await db.execute(
+        """
+        ALTER TABLE journal_entries ADD COLUMN meta TEXT DEFAULT '{}';
+        """
+    )
+
+
+async def m006_hierarchical_account_names(db):
+    """
+    Migrate account names to hierarchical Beancount-style format.
+    - "Cash" → "Assets:Cash"
+    - "Accounts Receivable" → "Assets:Receivable"
+    - "Food & Supplies" → "Expenses:Food:Supplies"
+    - "Accounts Receivable - af983632" → "Assets:Receivable:User-af983632"
+    """
+    from .account_utils import migrate_account_name
+    from .models import AccountType
+
+    # Get all existing accounts
+    accounts = await db.fetchall("SELECT * FROM accounts")
+
+    # Mapping of old names to new names
+    name_mappings = {
+        # Assets
+        "cash": "Assets:Cash",
+        "bank": "Assets:Bank",
+        "lightning": "Assets:Lightning:Balance",
+        "accounts_receivable": "Assets:Receivable",
+
+        # Liabilities
+        "accounts_payable": "Liabilities:Payable",
+
+        # Equity
+        "member_equity": "Equity:MemberEquity",
+        "retained_earnings": "Equity:RetainedEarnings",
+
+        # Revenue → Income
+        "accommodation_revenue": "Income:Accommodation",
+        "service_revenue": "Income:Service",
+        "other_revenue": "Income:Other",
+
+        # Expenses
+        "utilities": "Expenses:Utilities",
+        "food": "Expenses:Food:Supplies",
+        "maintenance": "Expenses:Maintenance",
+        "other_expense": "Expenses:Other",
+    }
+
+    # Update default accounts using ID-based mapping
+    for old_id, new_name in name_mappings.items():
+        await db.execute(
+            """
+            UPDATE accounts
+            SET name = :new_name
+            WHERE id = :old_id
+            """,
+            {"new_name": new_name, "old_id": old_id}
+        )
+
+    # Update user-specific accounts (those with user_id set)
+    user_accounts = await db.fetchall(
+        "SELECT * FROM accounts WHERE user_id IS NOT NULL"
+    )
+
+    for account in user_accounts:
+        # Parse account type
+        account_type = AccountType(account["account_type"])
+
+        # Migrate name
+        new_name = migrate_account_name(account["name"], account_type)
+
+        await db.execute(
+            """
+            UPDATE accounts
+            SET name = :new_name
+            WHERE id = :id
+            """,
+            {"new_name": new_name, "id": account["id"]}
+        )