feat: initial commit - finanzas app

Complete personal finance management application with:
- Dashboard with financial metrics and alerts
- Credit card management and payments
- Fixed and variable debt tracking
- Monthly budget planning
- Intelligent alert system
- Responsive design with Tailwind CSS

Tech stack: Next.js 14, TypeScript, Zustand, Recharts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

lib/store/slices/budgetSlice.ts

@@ -0,0 +1,39 @@
+import { StateCreator } from 'zustand'
+import { MonthlyBudget } from '@/lib/types'
+
+const now = new Date()
+
+export interface BudgetSlice {
+    monthlyBudgets: MonthlyBudget[]
+    currentMonth: number
+    currentYear: number
+
+    setMonthlyBudget: (budget: MonthlyBudget) => void
+    updateMonthlyBudget: (month: number, year: number, updates: Partial<MonthlyBudget>) => void
+}
+
+export const createBudgetSlice: StateCreator<BudgetSlice> = (set) => ({
+    monthlyBudgets: [],
+    currentMonth: now.getMonth() + 1,
+    currentYear: now.getFullYear(),
+
+    setMonthlyBudget: (budget) =>
+        set((state) => {
+            const existingIndex = state.monthlyBudgets.findIndex(
+                (b) => b.month === budget.month && b.year === budget.year
+            )
+            if (existingIndex >= 0) {
+                const newBudgets = [...state.monthlyBudgets]
+                newBudgets[existingIndex] = budget
+                return { monthlyBudgets: newBudgets }
+            }
+            return { monthlyBudgets: [...state.monthlyBudgets, budget] }
+        }),
+
+    updateMonthlyBudget: (month, year, updates) =>
+        set((state) => ({
+            monthlyBudgets: state.monthlyBudgets.map((b) =>
+                b.month === month && b.year === year ? { ...b, ...updates } : b
+            ),
+        })),
+})