fix: correct monthly actuals pre-population, void double-reversal, and cash flow history

- Monthly actuals grid now filters actual_amount to entry_type='monthly_actual'
  only, so other posted JEs in the same month don't bleed into the actuals UI
- Remove manual accounts.balance reversal from void() — the reversal JE's post()
  call already handles balance updates, preventing double-decrement per void
- Date void reversal entries to the original entry's date (not today) so
  historical monthly cash-flow periods stay accurate when actuals are re-edited
- Cash flow forecast now derives opening investment balances from investments
  purchased before the forecast start date rather than using current-snapshot
  totals, fixing historical months showing wrong investment balances

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/modules/journal-entries/journal-entries.service.ts

@@ -162,26 +162,18 @@ export class JournalEntriesService {
     if (!je.is_posted) throw new BadRequestException('Cannot void an unposted entry');
     if (je.is_void) throw new BadRequestException('Already voided');
 
-    // Reverse account balances
-    for (const line of je.lines) {
-      const debit = parseFloat(line.debit) || 0;
-      const credit = parseFloat(line.credit) || 0;
-      const reverseAmount = credit - debit;
-
-      await this.tenant.query(
-        `UPDATE accounts SET balance = balance + $1, updated_at = NOW() WHERE id = $2`,
-        [reverseAmount, line.account_id],
-      );
-    }
-
     await this.tenant.query(
       `UPDATE journal_entries SET is_void = true, voided_by = $1, voided_at = NOW(), void_reason = $2 WHERE id = $3`,
       [userId, reason, id],
     );
 
-    // Create reversing entry
+    // Create a reversing entry dated to the original entry's date so historical
+    // period balances stay accurate. The post() call handles accounts.balance updates —
+    // we do NOT manually reverse balances here to avoid double-counting.
     const reverseDto: CreateJournalEntryDto = {
-      entryDate: new Date().toISOString().split('T')[0],
+      entryDate: je.entry_date instanceof Date
+        ? je.entry_date.toISOString().split('T')[0]
+        : String(je.entry_date).split('T')[0],
       description: `VOID: ${je.description}`,
       referenceNumber: `VOID-${je.reference_number || je.id.slice(0, 8)}`,
       entryType: 'adjustment',

backend/src/modules/monthly-actuals/monthly-actuals.service.ts

@@ -38,6 +38,7 @@ export class MonthlyActualsService {
       LEFT JOIN journal_entry_lines jel ON jel.account_id = a.id
       LEFT JOIN journal_entries je ON je.id = jel.journal_entry_id
         AND je.is_posted = true AND je.is_void = false
+        AND je.entry_type = 'monthly_actual'
         AND EXTRACT(YEAR FROM je.entry_date) = $1
         AND EXTRACT(MONTH FROM je.entry_date) = $2
       WHERE a.is_active = true

backend/src/modules/reports/reports.service.ts

@@ -1089,9 +1089,25 @@ export class ReportsService {
       else projectIndex[key].reserve += cost;
     }
 
-    // Investment opening balances at start of period (approximate: use current values)
-    let runOpInv = opInv;
-    let runResInv = resInv;
+    // Investment balances at the start of the period — computed from the investment_accounts
+    // table as of startYear-01-01. We use current_value for all active investments that
+    // existed before startYear (purchase_date < startYear-01-01). Investments purchased
+    // after that date will be added when their purchase month is processed in the forecast loop.
+    const openingInvOp = await this.tenant.query(`
+      SELECT COALESCE(SUM(current_value), 0) as total
+      FROM investment_accounts
+      WHERE fund_type = 'operating' AND is_active = true
+        AND (purchase_date IS NULL OR purchase_date < $1::date)
+    `, [`${startYear}-01-01`]);
+    const openingInvRes = await this.tenant.query(`
+      SELECT COALESCE(SUM(current_value), 0) as total
+      FROM investment_accounts
+      WHERE fund_type = 'reserve' AND is_active = true
+        AND (purchase_date IS NULL OR purchase_date < $1::date)
+    `, [`${startYear}-01-01`]);
+
+    let runOpInv = parseFloat(openingInvOp[0]?.total || '0');
+    let runResInv = parseFloat(openingInvRes[0]?.total || '0');
 
     // Determine which months have actual journal entries
     // A month is "actual" only if it's not in the future AND has real journal entry data