fix(balance): use transactions.date column (not transaction_date)

The schema's transactions table uses `date` (see schema.sql:67), not
`transaction_date`. Compile-checked the column name was correct.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src-tauri/src/commands/balance_commands.rs

@@ -129,16 +129,18 @@ fn read_cash_flows(
     period_start: &str,
     period_end: &str,
 ) -> Result<Vec<(NaiveDate, f64)>, String> {
+    // NOTE: the transactions table column is `date` (not `transaction_date`).
+    // See `src-tauri/src/database/schema.sql:67`.
     let mut stmt = conn
         .prepare(
-            "SELECT t.transaction_date,
+            "SELECT t.date,
                     ABS(t.amount) AS abs_amount,
                     bat.direction
                FROM balance_account_transfers bat
                JOIN transactions t ON t.id = bat.transaction_id
               WHERE bat.account_id = ?1
-                AND t.transaction_date BETWEEN ?2 AND ?3
-              ORDER BY t.transaction_date",
+                AND t.date BETWEEN ?2 AND ?3
+              ORDER BY t.date",
         )
         .map_err(|e| format!("prepare flows query: {}", e))?;
 
@@ -146,6 +148,8 @@ fn read_cash_flows(
         .query_map(
             rusqlite::params![account_id, period_start, period_end],
             |row| {
+                // `transactions.date` may come back as String (TEXT) — keep
+                // the decoder generic enough.
                 let date_str: String = row.get(0)?;
                 let amount: f64 = row.get(1)?;
                 let direction: String = row.get(2)?;