Remove Ahorro from budget UI, add SALARY type and savings auto-accrual

Ahorro was already deducted from gross salary so displaying it in
budget projections was misleading. This removes the Ahorro card,
summary line, Proyecciones column, and Ahorro Anual card from the UI,
and strips all savings fields from budget API responses.

Adds SALARY TransactionType so salary deposits can be distinguished
from generic DEPOSITO transfers. When a SALARY transaction arrives,
the system auto-increments MEMP and MPAT savings account balances
(+200K CRC each) once per month via an idempotent accrual log.

New CRUD endpoints at /api/v1/savings-accrual/ allow manual correction
of the accrual history. Feb+Mar 2026 are seeded as historical baseline.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/budget/YearlyOverview.tsx

@@ -89,7 +89,6 @@ export default function YearlyOverview({
             <TableHead className="text-right">Egresos Fijos</TableHead>
             <TableHead className="text-right">Otros Gastos</TableHead>
             <TableHead className="text-right">Gran Total</TableHead>
-            <TableHead className="text-right">Ahorro</TableHead>
             <TableHead className="text-right">Acum. Anterior</TableHead>
             <TableHead className="text-right">Neto Mes</TableHead>
             <TableHead className="text-right">Balance Acum.</TableHead>
@@ -132,9 +131,6 @@ export default function YearlyOverview({
                 <TableCell data-sensitive className="text-right font-mono text-sm font-medium">
                   {formatAmount(m.gran_total_egresos, 'CRC')}
                 </TableCell>
-                <TableCell data-sensitive className="text-right font-mono text-sm text-muted-foreground">
-                  {formatAmount(m.projected_savings, 'CRC')}
-                </TableCell>
                 <TableCell
                   className={cn(
                     'text-right font-mono text-sm',