fix: migration crash 'no such column: undone' on old DBs

When migrateDB() upgraded the transactions table to add the 'waste'
CHECK constraint, the new table was created WITHOUT the 'undone' column.
The migration then tried to build idx_transactions_pid_type_undone, which
references 'undone' → PDOException SQLSTATE[HY000].

Fix:
- Add undone INTEGER DEFAULT 0 to the migration CREATE TABLE
- Replace 'INSERT INTO transactions SELECT * FROM transactions_old'
  with explicit column list (transactions_old may predate undone column)

Fixes: #56

api/database.php

@@ -138,11 +138,14 @@ function migrateDB(PDO $db): void {
                 quantity REAL NOT NULL,
                 location TEXT NOT NULL DEFAULT 'dispensa',
                 notes TEXT DEFAULT '',
+                undone INTEGER DEFAULT 0,
                 created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
                 FOREIGN KEY (product_id) REFERENCES products(id) ON DELETE CASCADE
             )
         ");
-        $db->exec("INSERT INTO transactions SELECT * FROM transactions_old");
+        // Insert with explicit columns: transactions_old may lack 'undone' (pre-v1.7.x DB)
+        $db->exec("INSERT INTO transactions (id, product_id, type, quantity, location, notes, created_at)
+                   SELECT id, product_id, type, quantity, location, notes, created_at FROM transactions_old");
         $db->exec("DROP TABLE transactions_old");
         $db->exec("CREATE INDEX IF NOT EXISTS idx_transactions_product ON transactions(product_id)");
         $db->exec("CREATE INDEX IF NOT EXISTS idx_transactions_date ON transactions(created_at)");