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/pages/Proyecciones.tsx

@@ -46,7 +46,7 @@ export default function Proyecciones() {
 
       {/* Annual summary cards */}
       {projection && (
-        <div className="grid gap-3 grid-cols-2 md:grid-cols-4">
+        <div className="grid gap-3 grid-cols-1 md:grid-cols-3">
           <Card>
             <CardContent className="pt-4 pb-3 px-4">
               <p className="text-xs text-muted-foreground">Ingresos Anuales</p>
@@ -63,14 +63,6 @@ export default function Proyecciones() {
               </p>
             </CardContent>
           </Card>
-          <Card>
-            <CardContent className="pt-4 pb-3 px-4">
-              <p className="text-xs text-muted-foreground">Ahorro Anual</p>
-              <p data-sensitive className="text-lg font-bold font-mono">
-                {formatAmount(projection.annual_savings, 'CRC')}
-              </p>
-            </CardContent>
-          </Card>
           <Card>
             <CardContent className="pt-4 pb-3 px-4">
               <p className="text-xs text-muted-foreground">Balance Neto Anual</p>